Coordinated by CRHEA-CNRS research laboratory, this monthly newsletter is produced by Knowmade with collaboration from the managers of GANEX groups. The newsletter presents a selection of newest scientific publications, patent applications and press releases related to III-Nitride semiconductor materials (GaN, AlN, InN and alloys)

All issues on www.ganex.fr in Veille section. Free subscription http://www.knowmade.com/ganex

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Cluster of Excellence (Labex, 2012-2019) GANEX is a cluster gathering French research teams involved in GaN technology. The objective of GANEX is to strengthen the position of French academic players in terms of knowledge and visibility, and reinforce the French industrials in terms of know-how and market share. www.ganex.fr

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GANEX Newsletter No. 31-32 August - September 2015

III-N Technology

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METHODOLOGY

Each month

250+ new scientific publications

120+ new patent applications

20+ new press releases

Sources 10+ scientific journal editors

Elsevier, IOP, IEEE, Wiley, Springer, APS, AIP, AVS, ECS, Nature, Science …

10+ specialist magazines Semiconductor Today, ElectoIQ, i-micronews,

Compound Semiconductor, Solid State Technology … 5+ open access database: FreeFulPDF, DOAJ …

Patent database: Questel-Orbit

Selection by III-N French

experts

GANEX monthly newsletter

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TABLE OF CONTENTS (clickable links to chapters)

SCIENTIFIC PUBLICATION ................................................................................................................... 4

GROUP 1 - LEDs and Lighting ................................................................................................................... 4

GROUP 2 - Laser and Coherent sources ................................................................................................. 11

GROUP 3 - Power Electronics ................................................................................................................. 14

GROUP 4 - Advanced Electronics and RF ............................................................................................... 21

GROUP 5 - Sensors and MEMS ............................................................................................................... 29

GROUP 6 - Photovoltaics and Energy harvesting ................................................................................... 33

GROUP 7 - Materials, Technology and Fundamental............................................................................. 35

PRESS RELEASE ................................................................................................................................ 52

PATENT APPLICATION ...................................................................................................................... 74

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SCIENTIFIC PUBLICATION Selection of new scientific articles

GROUP 1 - LEDs and Lighting Group leader: Benjamin Damilano (CRHEA-CNRS)

Information selected by Benjamin Damilano (CRHEA-CNRS)

Enhanced performance characteristics of n-ZnO/p-GaN heterojunction light-emitting diodes by forming excellent Ohmic contact to p-GaN Seonghoon Jeong, Hyunsoo Kim School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk National University, Jeonju 561-756, Korea Materials Science in Semiconductor Processing Volume 39, November 2015, Pages 771–774 http://dx.doi.org/10.1016/j.mssp.2015.06.045

We report significantly improved performance characteristics of n-ZnO/p-GaN heterojunction light-emitting diodes (LEDs) by forming excellent Ohmic contact to p-GaN. An elaborately designed fabrication procedure to suppress ZnO sputtering damage on p-GaN, i.e., a selective SiO2 passivation of the p-GaN surface, was shown to yield excellent Ohmic contact to p-GaN with a specific contact resistance of 9.8×10−3 Ω cm2, while the reference contact formed on non-protected p-GaN showed non-Ohmic behavior. Heterojunction LEDs fabricated with the improved p-Ohmic contact had much better performance characteristics than did the reference LEDs, i.e., the forward voltages at 2 mA were 5.6 and 16.2 V, the series resistances were 404 and 1693 Ω, and the optical output powers at 3 mA were 56.4 and 19.9 μW for the developed and reference LEDs, respectively. InGaN light-emitting diodes with embedded nanoporous GaN distributed Bragg reflectors Bing-Cheng Shieh1, Yuan-Chang Jhang1, Kun-Pin Huang1, Wan-Chun Huang1, Jing-Jie Dai1, Chun-Feng Lai2 and Chia-Feng Lin1 1 Department of Materials Science and Engineering, National Chung Hsing University, Taichung 402, Taiwan 2 Department of Photonics, Feng Chia University, Taichung 40724, Taiwan Applied Physics Express Vol. 8; 082101

http://dx.doi.org/10.7567/APEX.8.082101

InGaN-based light-emitting diodes (LEDs) with embedded conductive nanoporous GaN/undoped GaN (NP-GaN/u-GaN) distributed Bragg reflectors (DBRs) were demonstrated. Nanoporous GaN DBR structures were fabricated by pulsed 355 nm laser scribing and electrochemical etching processes. Heavily Si-doped n-type GaN:Si layers (n+-GaN) in an eight-period n+-GaN/u-GaN stack structure were transformed into a low-refractive-index, conductive nanoporous GaN structure. The measured center wavelength, peak reflectivity, and bandwidth of the nanoporous GaN DBR structure were 417 nm, 96.7%, and 34 nm, respectively. Resonance cavity modes of the photoluminescence spectra were observed in the treated LED structure with the nanoporous DBR structure. How to decide between competing efficiency droop models for GaN-based light-emitting diodes Joachim Piprek1,a) 1 NUSOD Institute LLC, Newark, Delaware 19714-7204, USA Applied Physics Letters Vol. 107, 022107 (2015) http://dx.doi.org/10.1063/1.4927202

GaN-based light-emitting diodes (LEDs) exhibit a strong efficiency droop with higher current injection, which has been mainly attributed to Auger recombination and electron leakage, respectively. Thus far, the few reports on direct measurements of these two processes do not confirm their dominating influence on the droop unambiguously. Advanced numerical simulations of experimental characteristics are shown to validate one or the other explanation by variation of uncertain material parameters. We finally demonstrate how the comparative simulation of

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temperature effects enables a clear distinction between both models. Contrary to common assumptions, the consistently measured efficiency reduction of blue LEDs with higher ambient temperature eliminates electron leakage as primary cause of the efficiency droop in these devices. Transport and capture properties of Auger-generated high-energy carriers in (AlInGa)N quantum well structures A. Nirschl1,2,a), M. Binder1, M. Schmid1, M. M. Karow1,b), I. Pietzonka1, H.-J. Lugauer1, R. Zeisel1, M. Sabathil1, D. Bougeard2 and B. Galler1 1 OSRAM Opto Semiconductors GmbH, Leibnizstraße 4, 93055 Regensburg, Germany 2 Institut für Experimentelle und Angewandte Physik, Universität Regensburg, Universitätsstraße 31, 93040 Regensburg, Germany Journal of Applied Physics Vol. 118, 033103 (2015) http://dx.doi.org/10.1063/1.4927154

Recent photoluminescence experiments presented by M. Binder et al. [Appl. Phys. Lett. 103, 071108 (2013)] demonstrated the visualization of high-energy carriers generated by Auger recombination in (AlInGa)N multi quantum wells. Two fundamental limitations were deduced which reduce the detection efficiency of Auger processes contributing to the reduction in internal quantum efficiency: the transfer probability of these hot electrons and holes in a detection well and the asymmetry in type of Auger recombination. We investigate the transport and capture properties of these high-energy carriers regarding polarization fields, the transfer distance to the generating well, and the number of detection wells. All three factors are shown to have a noticeable impact on the detection of these hot particles. Furthermore, the investigations support the finding that electron-electron-hole exceeds electron-hole-hole Auger recombination if the densities of both carrier types are similar. Overall, the results add to the evidence that Auger processes play an important role in the reduction of efficiency in (AlInGa)N based LEDs.

Efficient carrier relaxation and fast carrier recombination of N-polar InGaN/GaN light emitting diodes Shih-Wei Feng1,a), Po-Hsun Liao1, Benjamin Leung2, Jung Han2, Fann-Wei Yang3 and Hsiang-Chen Wang4 1 Department of Applied Physics, National University of Kaohsiung, No. 700, Kaohsiung University Rd., Nan Tzu Dist., 811 Kaohsiung, Taiwan 2 Department of Electrical Engineering, Yale University, New Haven, Connecticut 06520, USA 3 Department of Electronic Engineering, Southern Taiwan University of Science and Technology, Tainan, Taiwan 4 Graduate Institute of Opto-Mechatronics and Advanced Institute of Manufacturing with High-Tech Innovations (AIM-HI), National Chung Cheng University, Chia-Yi, Taiwan Journal of Applied Physics Vol. 118, 043104 (2015) http://dx.doi.org/10.1063/1.4927421

Based on quantum efficiency and time-resolved electroluminescence measurements, the effects of carrier localization and quantum-confined Stark effect (QCSE) on carrier transport and recombination dynamics of Ga- and N-polar InGaN/GaN light-emitting diodes (LEDs) are reported. The N-polar LED exhibits shorter ns-scale response, rising, delay, and recombination times than the Ga-polar one does. Stronger carrier localization and the combined effects of suppressed QCSE and electric field and lower potential barrier acting upon the forward bias in an N-polar LED provide the advantages of more efficient carrier relaxation and faster carrier recombination. By optimizing growth conditions to enhance the radiative recombination, the advantages of more efficient carrier relaxation and faster carrier recombination in a competitive performance N-polar LED can be realized for applications of high-speed flash LEDs. The research results provide important information for carrier transport and recombination dynamics of an N-polar InGaN/GaN LED.

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Light-extraction efficiency control in AlGaN-based deep-ultraviolet flip-chip light-emitting diodes: a comparison to InGaN-based visible flip-chip light-emitting diodes Keon Hwa Lee,1,2 Hyun Jung Park,3 Seung Hwan Kim,2 Mojtaba Asadirad,4 Yong-Tae Moon,1 Joon Seop Kwak,3,6 and Jae-Hyun Ryou2,4,5,* 1Department of LED Business, LG Innotek Company, Paju 413-901, South Korea 2Department of Mechanical Engineering, University of Houston, Houston, TX 77204-4006, USA 3Department of Printed Electronics Engineering, Sunchon National University, Jeonnam 540-742, South Korea 4Materials Science and Engineering Program, University of Houston, Houston, TX 77204, USA 5Texas Center for Superconductivity at the University of Houston (TcSUH), Houston, TX 77204, USA Optics Express Vol. 23, Issue 16, pp. 20340-20349 (2015) http://dx.doi.org/10.1364/OE.23.020340

We study light-extraction efficiency (LEE) of AlGaN-based deep-ultraviolet light-emitting diodes (DUV-LEDs) using flip-chip (FC) devices with varied thickness in remaining sapphire substrate by experimental output power measurement and computational methods using 3-dimensional finite-difference time-domain (3D-FDTD) and Monte Carlo ray-tracing simulations. Light-output power of DUV-FCLEDs compared at a current of 20 mA increases with thicker sapphire, showing higher LEE for an LED with 250-μm-thick sapphire by ~39% than that with 100-μm-thick sapphire. In contrast, LEEs of visible FCLEDs show only marginal improvement with increasing sapphire thickness, that is, ~6% improvement for an LED with 250-μm-thick sapphire. 3D-FDTD simulation reveals a mechanism of enhanced light extraction with various sidewall roughness and thickness in sapphire substrates. Ray tracing simulation examines the light propagation behavior of DUV-FCLED structures. The enhanced output power and higher LEE strongly depends on the sidewall roughness of the sapphire substrate rather than thickness itself. The thickness starts playing a role only when the sapphire sidewalls become rough. The roughened surface of sapphire sidewall during chip-separation process is critical for TM-polarized photons from AlGaN quantum

wells to escape in lateral directions before they are absorbed by p-GaN and Au-metal. Furthermore, the ray tracing results show a reasonably good agreement with the experimental result of the LEE. InGaN based micro light emitting diodes featuring a buried GaN tunnel junction M. Malinverni1,a), D. Martin1 and N. Grandjean1 1 ICMP, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland Applied Physics Letters Vol. 107, 051107 (2015) http://dx.doi.org/10.1063/1.492803

GaN tunnel junctions (TJs) are grown by ammonia molecular beam epitaxy. High doping levels are achieved with a net acceptor concentration close to ∼1020 cm−3, thanks to the low growth temperature. This allows for the realization of p-n junctions with ultrathin depletion width enabling efficient interband tunneling. n-p-n structures featuring such a TJ exhibit low leakage current densities, e.g., <5 × 10−5 A cm−2 at reverse bias of 10 V. Under forward bias, the voltage is 3.3 V and 4.8 V for current densities of 20 A cm−2 and 2000 A cm−2, respectively. The specific series resistance of the whole device is 3.7 × 10−4 Ω cm2. Then micro-light emitting diodes (μ-LEDs) featuring buried TJs are fabricated. Excellent current confinement is demonstrated together with homogeneous electrical injection, as seen on electroluminescence mapping. Finally, the I-V characteristics of μ-LEDs with various diameters point out the role of the access resistance at the current aperture edge. Modification of internal quantum efficiency and efficiency droop in GaN-based flip-chip light-emitting diodes via the Purcell effect Han-Youl Ryu Department of Physics, Inha University, 100 Inha-ro, Nam-gu, Incheon 402-751, South Korea Optics Express Vol. 23, Issue 19, pp. A1157-A1166 (2015) http://dx.doi.org/10.1364/OE.23.0A1157

The Purcell effect in GaN-based flip-chip (FC) light-emitting diode (LED) structures is investigated

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numerically using finite-difference time-domain simulations. Depending on the thickness of the p-GaN layer, the variation of the Purcell factor of FC LEDs is obtained to be as high as 20%, which results in the relative modification of the internal quantum efficiency (IQE) as large as 8% and 2.5% for the unmodified IQE of 0.4 and 0.8, respectively. Since the influence of the Purcell effect becomes more conspicuous as the IQE decreases, the Purcell enhancement can be advantageously used to mitigate the efficiency droop problem to some extent. When the Purcell effect is positively applied to the blue LED with the peak IQE of 0.8 and the droop ratio of 29.1%, the peak IQE and the droop ratio are found to be improved to 0.82 and 26.3%. This small but non-negligible effect on IQE is expected to be importantly adopted for industry development of high efficiency LEDs. The beneficial effects of a p-type GaInN spacer layer on the efficiency of GaInN/GaN light-emitting diodes Guan-Bo Lina, Xiaoguang Zhangb, Soo Min Leeb, George Papasouliotisb, Jong Kyu Kimc, E. Fred Schuberta, Jaehee Chod a Future Chips Constellation, Department of Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA b Veeco MOCVD Operations, Somerset, NJ 08873, USA c Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea d School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk National University, Jeonju 561-756, Republic of Korea Current Applied Physics http://dx.doi.org/10.1016/j.cap.2015.07.009

Light-emitting diodes (LEDs) with a Mg-doped p-type Ga1−xInxN (0 ≤ x ≤ 0.07) spacer layer located between an undoped GaN spacer layer and the electron blocking layer are investigated. The LEDs are found to have comparable peak efficiency but less efficiency droop when the crystal quality of the p-type Ga1−xInxN spacer layer is well-controlled by lowering the growth temperature and by using a suitable In composition and Mg doping concentration. All LED samples with the p-type spacer layer show a smaller efficiency droop

compared to a reference LED having an undoped GaN spacer. Among the sample sets investigated, an optical power enhancement of 12% at 111 A/cm2 is obtained when inserting a 5 nm-thick p-type Ga0.97In0.03N spacer layer. The results support that carrier transport is the key factor in the efficiency droop observed in GaN-based LEDs. Failure causes and mechanisms of retrofit LED lamps C. De Santi, M. Dal Lago, M. Buffolo, D. Monti, M. Meneghini, G. Meneghesso, E. Zanoni Department of Information Engineering, University of Padova, Padova, Italy Microelectronics Reliability http://dx.doi.org/10.1016/j.microrel.2015.06.080

This paper describes one of the first studies of the degradation of retrofit light bulbs based on white GaN light emitting diodes. The results indicate that the lifetime of LED lamps depends mostly on the stability of the driver and optical elements, rather than on the degradation of the LED chips, that have a stable output over stress time. By comparing lamps from four different manufacturers stressed at room and high temperature, we found that (i) long-term stress causes a change of the chromatic properties of the lamps, which is ascribed to the degradation of the phosphors or to the inner LED reflector; (ii) during aging the LED driver may degrade gradually and/or catastrophically, causing a reduction of the output optical power, or a complete failure; (iii) proper thermal management and heat dissipation reduce the degradation rate; (iv) spectral transmissivity measurements and visual inspection reveal the degradation of the diffusive optical elements, which is induced by the short wavelength side of the LED emission spectrum. Growth of nitride-based light emitting diodes with a high-reflectivity distributed Bragg reflector on mesa-patterned silicon substrate Benjamin Damilano, Stéphane Brochen, Julien Brault, Tasnia Hossain, François Réveret, Eric Frayssinet, Sébastien Chenot, Aimeric Courville, Yvon Cordier and Fabrice Semond 1CRHEA-CNRS UPR10, Centre de Recherche sur l'Hétéro-Epitaxie et ses Applications, Centre National de la Recherche Scientifique, 06560 Valbonne, France

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2Département de Physique, Université de Nice Sophia-Antipolis, Parc Valrose, 28 av. Valrose, 06108 Nice cedex 2, France 3Institut Pascal UMR 6622, CNRS, Université Blaise Pascal, 24 avenue des landais, 63177 Aubière cedex, France Physica status solidi (a) http://dx.doi.org/10.1002/pssa.201532303

(Ga,In)N/GaN multiple quantum well blue light emitting diodes (LEDs) grown on mesa-patterned silicon substrates with improved electro-optic characteristics are demonstrated. The active regions are grown on top of high-reflectivity AlN/(Al,Ga)N distributed Bragg reflectors (DBRs). Due to efficient stress relaxation at the mesa edges, crack formation during growth or upon the post-growth cooling-down of the samples can be avoided. A large number of AlN/(Al,Ga)N bilayers in the DBR can be then included in the LED structures leading to strong enhancement of the LED device output power in spite of the presence of the absorbing silicon substrate at the LED emission wavelength. Photothermal activated failure mechanism in polymer-based packaging of low power InGaN/GaN MQW LED under active storage Raphael Baillot, Yannick Deshayes, Yves Ousten, Laurent Bechou IMS Laboratory, University of Bordeaux, UMR 5218, F-33400 Talence, France Microelectronics Reliability http://dx.doi.org/10.1016/j.microrel.2015.06.145

GaN-based LEDs often use polymer material as chip coating. The most used polymer coatings are siloxane-based materials such as poly(methyl-phenyl-silixane) – PMPS – or poly(dimethylsiloxane) — PDMS. Although their thermal properties offer great possibilities to justify their integration in optoelectronic devices, pellicular effect may occur. This paper points out a pellicular failure mechanism occurring in MQW GaN-based LED submitted to active storage (1500 h/30 mA/85 °C) determined from their environment stresses. Before aging, an absorption/reemission fluorescence process has

been extracted. By performing fluorescence analysis, we have found out the cause of such mechanism coming from silicone oil (polymer coating). Additional physico-chemical analyses, consisting of 1H NMR and MALDI-TOF mass spectrometry, have been investigated to work out the origin of the absorption/reemission process. The presence of low molecular weight molecules (LMWM) playing the role of fluorophore molecules is responsible for it. After aging, 65% optical power losses have been reported. A combination of electro-optical characterizations and physico-chemical analyses has led to the main failure mechanism extraction that is the molecular change of silicone oil activated by photothermal phenomenon. Such pellicular failure mechanism has been suggested to be linked to polymerization or cross-linking of silicone oil usually present in GaN-based LEDs. Onset of the Efficiency Droop in GaInN Quantum Well Light-Emitting Diodes under Photoluminescence and Electroluminescence Excitation Guan-Bo Lin *†, E. Fred Schubert †, Jaehee Cho *‡, Jun Hyuk Park §, and Jong Kyu Kim § † Department for Electrical, Computer, and Systems Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180, United States ‡ School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk National University, Jeonju 561-756, Republic of Korea § Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Gyeongbuk 790-784, Republic of Korea ACS Photonics http://dx.doi.org/10.1021/acsphotonics.5b00305

The efficiency of Ga0.87In0.13N/GaN single and multiple quantum well (QW) light-emitting diodes is investigated under photoluminescence (PL) and electroluminescence (EL) excitation. By measuring the laser spot area (knife-edge method) and the absorbance of the GaInN QW (transmittance/reflectance measurements), the PL excitation density can be converted to an equivalent EL excitation density. The EL efficiency droop-onset occurs at an excitation density of 2.08 × 1026 cm–3 s–1 (J = 10 A/cm2), whereas no

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PL efficiency droop is found for excitation densities as high as 3.11 × 1027 cm–3 s–1 (J = 149 A/cm2). Considering Shockley–Read–Hall, radiative, and Auger recombination and including carrier leakage shows that the EL efficiency droop is consistent with a reduction of injection efficiency. Uniformity investigation of MOCVD-grown LED layers Zhimin Jiang1, Han Yan3, Sheng Liu2,4, Zhi Zhang1, Zhiyin Gan2,6,* and Haisheng Fang1,5 1School of Energy and Power Engineering, Huazhong University of Science&Techology, Wuhan, Hubei, China 2School of Mechanical Science and Engineering, Huazhong University of Science &Techology, Wuhan, Hubei, China 3School of Mechanical and Electronic Engineering, Wuhan University of Technology, Wuhan, Hubei, China 4School of Power and Mechanical Engineering, Wuhan University, Wuhan, China 5Wuhan National Lab for Optoelectronics, Huazhong University of Science &Techology, Wuhan, Hubei 6Guangdong RealFaith Semiconductor Equipment Co., Ltd, Foshan, Guangdong, China Crystal Research and Technology http://dx.doi.org/10.1002/crat.201500135

Doped or undoped gallium nitride compounds (GaN/InGaN), usually grown by metal-organic chemical vapor deposition (MOCVD) method, are at the heart of blue and green light emitting diodes (LEDs). Growth uniformities, such as the excited wavelength, luminous intensity and film thickness, critically influence their application in LED devices. In this paper, growth of GaN compounds in a MOCVD reactor, capable of a one-time production of 36 × 2” wafers of nitrides, has been investigated. To examine growth uniformity across the wafer and from wafer to wafer, the reactor is divided into Zone A, Zone B and Zone C according to distance to the center of the graphite susceptor. Comparative analysis of each zone offers a straightforward view of the mean excitation wavelength, luminous intensity, film thickness and their standard deviations. Conformity of the growth uniformity in each zone is further checked comprehensively through averaging across-wafer and wafer-to-wafer variables and their standard deviations. Zone B is

found to retain excellent wavelength uniformity, since it is located at the middle of the susceptor with weaker effects of the susceptor edge and of the inlet gas flow. Zone A, at the center of the reactor, has the best mean intensity and thickness uniformities due to a well control of the infrared temperature measurement during the growth. And Zone C is worst in all uniformities and should be the main focus when optimizing the reactor. The above experimental analysis reveals the principles common to the MOCVD technique, and provides a basic for further optimization of the process window to improve the cycles with considerable reduction of the costs. High brightness GaN-on-Si based blue LEDs grown on 150 mm Si substrates using thin buffer layer technology Zhang, L. Tan, W.S. ; Westwater, S. ; Pujol, A. ; Pinos, A. ; Mezouari, S. ; Stribley, K. ; Whiteman, J. ; Shannon, J. ; Strickland, K. Plessey Semiconductors Ltd, Tamerton Road, Plymouth, PL6 7BQ, United Kingdom. Electron Devices Society, IEEE Journal of the http://dx.doi.org/10.1109/JEDS.2015.2463738

The commercial adoption of GaN-on-Si LED chip technology is lagging behind incumbent sapphire substrates due to significantly longer growth time and poorer crystalline quality. To address these challenges, we report on the growth of high-quality crack-free InGaN/GaN LED structure on 150 mm Si (111) substrate using thin buffer layer technology. The total epilayer thickness is only 3.75 ???m, offering significant growth time savings and faster manufacturing process throughput. A SiNx interlayer is inserted in the buffer layer to promote lateral overgrowth and improve material quality, resulting in full width at half maximum <0002> and <10-12> of 380 arcsec and 390 arcsec, respectively. Reducing dislocation density and optimizing KOH roughening of the n-GaN layer is found to be critical towards improving device performance. The devices were processed as 1 x 1 mm2 vertical thin film dies and mounted into a conventional 3535 package with silicone dome lens. The result is a light output power of 563 mW and an operating voltage of 3.05 V, corresponding to a wall-plug-efficiency of 52.7% when driven at 350 mA. These results

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attest the feasibility of thin buffer GaN-on-Si technology for solid state lighting applications. Thermally Engineered Flip-chip InGaN/GaN Well-ordered Nanocolumn Array LEDs Hayashi, H. Fukushima, D. ; Noma, T. ; Tomimatsu, D. ; Konno, Y. ; Mizuno, M. ; Kishino, K. Sophia University, 7-1 Kioi-cho, Chiyoda-ku, Tokyo 102-8554, Japan Photonics Technology Letters, IEEE http://dx.doi.org/10.1109/LPT.2015.2463756

Thermally engineered flip-chip (FC) InGaN/GaN well-ordered nanocolumn array light-emitting diodes (LEDs) are demonstrated for the first time. A directional photoluminescence beam profile was observed from the n-side bottom of the GaN nanocolumns, which maintained an optically damage-free periodic arrangement of nanocolumns through the FC process involving Si substrate removal by wet etching. The developed LED achieved single-peak emission at approximately 570 nm in the middle of the visible range. The thermal resistance of the nanocolumn LED was significantly reduced using the FC configuration. Color Conversion of GaN-Based Micro Light-Emitting Diodes Using Quantum Dots Lee, C. Cheng, C. ; Lee, H. ; Chu, Y. ; Fang, Y. ; Chao, C. ; Wu, M. Institute of Microelectronics, Department of Electrical Engineering, Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan. Photonics Technology Letters, IEEE http://dx.doi.org/10.1109/LPT.2015.2462072

Using CdSe/ZnS quantum dots (QDs) excited by the blue light emission of GaN-based micro light-emitting diodes (LEDs), quasi-monochromatic red light sources with emission wavelength of 625 nm were obtained. In order to enhance the blue light emission of GaN-based LEDs for further excitation of QDs, distributed/hybrid Bragg reflectors and zinc-oxide (ZnO) nanorod array were respectively introduced to the top/bottom and top sides of GaN-based micro LEDs. The presence of ZnO

nanorod array helps to channel the blue light to pump the CdSe/ZnS QDs for enhancing the red light emission. The electroluminescence of micro QDs-LEDs with reflectors and ZnO nanorod array was increased by 57.4% compared to the micro QDs-LEDs alone. The CIE chromaticity coordinate of the micro QDs-LEDs with reflectors and ZnO nanorod array was very close to the red light emission at (0.59, 0.26).

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GROUP 2 - Laser and Coherent sources Group leader: Bruno Gayral (CEA)

Information selected by Knowmade

Nonpolar III-nitride vertical-cavity surface-emitting lasers incorporating an ion implanted aperture J. T. Leonard1,a), D. A. Cohen1, B. P. Yonkee1, R. M. Farrell1, T. Margalith1, S. Lee2, S. P. DenBaars1,2, J. S. Speck1 and S. Nakamura1,2 1 Materials Department, University of California, Santa Barbara, California 93106, USA 2 Department of Electrical and Computer Engineering, University of California, Santa Barbara, California 93106, USA Applied Physics Letters Vol. 107, 011102 (2015); http://dx.doi.org/10.1063/1.4926365

We report on our recent progress in improving the performance of nonpolar III-nitride vertical-cavity surface-emitting lasers (VCSELs) by using an Al ion implanted aperture and employing a multi-layer electron-beam evaporated ITO intracavity contact. The use of an ion implanted aperture improves the lateral confinement over SiNx apertures by enabling a planar ITO design, while the multi-layer ITO contact minimizes scattering losses due to its epitaxially smooth morphology. The reported VCSEL has 10 QWs, with a 3 nm quantum well width, 1 nm barriers, a 5 nm electron-blocking layer, and a 6.95- λ total cavity thickness. These advances yield a single longitudinal mode 406 nm nonpolar VCSEL with a low threshold current density (∼16 kA/cm2), a peak output power of ∼12 μW, and a 100% polarization ratio. The lasing in the current aperture is observed to be spatially non-uniform, which is likely a result of filamentation caused by non-uniform current spreading, lateral optical confinement, contact resistance, and absorption loss. Continuous and dynamic spectral tuning of single nanowire lasers with subnanometer resolution using hydrostatic pressure Sheng Liu,*ab Changyi Li,c Jeffrey J. Figiel,a Steven R. J. Brueck,c Igal Brenerab and George T. Wang*a a Sandia National Laboratories, Albuquerque, USA

b Center for Integrated Nanotechnologies, Sandia National Laboratories, Albuquerque, USA c Center for High Technology Materials, University of New Mexico, 1313 Goddard St. SE, Albuquerque, USA Nanoscale 2015,7, 9581-9588 http://dx.doi.org/10.1039/C5NR01855B

We report continuous, dynamic, reversible, and widely tunable lasing from 367 to 337 nm from single GaN nanowires (NWs) by applying hydrostatic pressure up to ∼7 GPa. The GaN NW lasers, with heights of 4–5 μm and diameters ∼140 nm, are fabricated using a lithographically defined two-step top-down technique. The wavelength tuning is caused by an increasing Γ direct bandgap of GaN with increasing pressure and is precisely controllable to subnanometer resolution. The observed pressure coefficients of the NWs are ∼40% larger compared with GaN microstructures fabricated from the same material or from reported bulk GaN values, revealing a nanoscale-related effect that significantly enhances the tuning range using this approach. This approach can be generally applied to other semiconductor NW lasers to potentially achieve full spectral coverage from the UV to IR. Pulsed electron-beam-pumped laser based on AlGaN/InGaN/GaN quantum-well heterostructure N A Gamov1, E V Zhdanova1, M M Zverev1, D V Peregudov1, V B Studenov1, A V Mazalov2, V A Kureshov2, D R Sabitov2, A A Padalitsa2 and A A Marmalyuk2,3 1 Moscow State Institute of Radio-Engineering, Electronics and Automation (Technical University), Moscow, Russian Federation 2 Open Joint-Stock Company M.F. Stel'makh Polyus Research Institute, Moscow, Russia 3 National Research Nuclear University ""MEPhI"", Moscow Quantum Electronics Vol. 45; 601

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http://dx.doi.org/10.1070/QE2015v045n07ABEH015780

The parameters of pulsed blue-violet (λ ≈ 430 nm at T = 300 K) lasers based on an AlGaN/InGaN/GaN structure with five InGaN quantum wells and transverse electron-beam pumping are studied. At room temperature of the active element, the minimum electron energy was 9 keV and the minimum threshold electron beam current density was 8 A cm-2 at an electron energy of 18 keV. GaN-Diode-Laser-Pumped Optical Parametric Generation in Nonlinear Waveguide HWANHONG LIM, Sunao Kurimura, Kazufumi Fujii Masayuki Okano, Shigeki Takeuchi Kyoto University, JapanNational Institute for Materials Science, Japan; Nonlinear Optics paper NTu1B.3 http://dx.doi.org/10.1364/NLO.2015.NTu1B.3

We demonstrated optical parametric generation (OPG) pumped by GaN diode laser in nonlinear optical waveguide. Mg:SLT-based slab waveguide emits visible photons with RGB spectrum and degenerate photon pairs in 800 nm region with controlled bandwidth. An electrically injected AlGaN nanowire laser operating in the ultraviolet-C band S. Zhao1, X. Liu1, S. Y. Woo2, J. Kang1, G. A. Botton2 and Z. Mi1,a 1 Department of Electrical and Computer Engineering, McGill University, 3480 University Street, Montreal, Quebec H3A 0E9, Canada 2 Department of Materials Science and Engineering, Canadian Centre for Electron Microscopy, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1, Canada Applied Physics Letters Vol. 107, 043101 (2015); http://dx.doi.org/10.1063/1.4927602

We have investigated the molecular beam epitaxial growth and characterization of nearly defect-free AlGaN nanowire heterostructures grown directly on Si substrate. By exploiting the Anderson localization of light, we have

demonstrated electrically injected AlGaN nanowire lasers that can operate at 262.1 nm. The threshold current density is 200 A/cm2 at 77 K. The relatively low threshold current is attributed to the high Q-factor of the random cavity and the three-dimensional quantum confinement offered by the atomic-scale composition modulation in self-organized AlGaN nanowires. Embedded GaN nanostripes on c-sapphire for DFB lasers with semipolar quantum wells Robert A. R. Leute1,*, Dominik Heinz1, Junjun Wang1, Tobias Meisch1, Marcus Müller2, Gordon Schmidt2, Sebastian Metzner2, Peter Veit2, Frank Bertram2, Jürgen Christen2, Martin Martens3, Tim Wernicke3, Michael Kneissl3, Stefan Jenisch4, Steffen Strehle4, Oliver Rettig5, Klaus Thonke5 and Ferdinand Scholz1 1Institute of Optoelectronics, Ulm University, Ulm, Germany 2Institute of Experimental Physics, Otto-von-Guericke-University, 39106 Magdeburg, Germany 3Institute of Solid State Physics, Technical University of Berlin, Berlin, Germany 4Institute of Electron Devices and Circuits, Ulm University, Ulm, Germany 5Institute of Quantum Matter / Semiconductor Physics Group, Ulm University, Ulm, Germany Physica status solidi (b) http://dx.doi.org/10.1002/pssb.201552277

GaN based laser diodes with semipolar quantum wells are typically grown on free-standing pseudo-substrates of small size. We present an approach to create a distributed-feedback (DFB) laser with semipolar quantum wells (QWs) on c-oriented templates. The templates are based on 2-inch sapphire wafers, the method could easily be adapted to larger diameters which are available commercially. GaN nanostripes with triangular cross-section are grown by selective area epitaxy (SAE) and QWs are grown on their semipolar side facets. The nanostripes are completely embedded and can be sandwiched inside a waveguide. For optical pumping, open waveguide structures with only a bottom cladding are used. Using nanoimprint lithography, stripe masks with 250 nm periodicity were fabricated over the whole wafer area. The periodicity corresponds to a 3rd order DFB structure for a laser emitting in the blue wavelength regime. These samples were

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analyzed structurally by high-resolution transmission electron microscopy (HRTEM), and spatio-spectrally by cathodoluminescence (CL) inside a scanning transmission electron microscope (STEM). Samples with an undoped cap are pumped optically for stimulated emission. To prove the feasibility of realizing a 2nd order DFB structure with this approach, stripes with a 170 nm periodicity are fabricated by electron beam lithography and SAE. Second harmonic generation in a GaN photonic crystal cavity on silicon Zeng, Y. ; Roland, I. ; Checoury, X. ; Han, Z. ; Kurdi, M.El ; Sauvage, S. ; Gayral, B. ; Brimont, C. ; Guillet, T. ; Mexis, M. ; Semond, F. ; Boucaud, P. Institut d'Electronique Fondamentale, CNRS - Univ. Paris Sud 11, Bailment 220, F-91405 Orsay, France Lasers and Electro-Optics (CLEO), 2015 Conference on http://dx.doi.org/10.1364/CLEO_SI.2015.STu2I.4

We report on second harmonic generation in a free-standing gallium nitride photonic crystal cavity fabricated on a silicon substrate. The cavity is resonant at 1577 nm and the harmonic conversion is obtained with a continuous wave laser. High resolution spatial imaging of the second harmonic field allows us to make the correlation between the harmonic emission pattern and the dominating second order polarization Pz. Wavelength Selection and Polarization Multiplexing of Blue Laser Diodes Byrd, M. ; Pung, A. ; Johnson, E. ; Lee, K. ; Magnusson, R. ; Binun, P. ; McCormick, K. " Department of Electrical and Computer Engineering, Clemson University, Clemson, SC 29634 USA Photonics Technology Letters, IEEE http://dx.doi.org/10.1109/LPT.2015.2455876

An external laser cavity was constructed that utilizes polarization multiplexing to combine the emission from two Gallium nitride blue laser diodes. A polarization dependent narrow band resonant mirror was designed to be the output coupler of this cavity, which locked both laser diodes at a fixed wavelength of 445.5 nm with a

line-width of less than 0.5 nm. Output powers from this system approached 0.7 W while maintaining complete spectral control. Annular-Shaped Emission from Gallium Nitride Nanotube Lasers Changyi Li †, Sheng Liu ‡§, Antonio Hurtado ∥, Jeremy B. Wright †‡, Huiwen Xu †, Ting Shan Luk ‡§, Jeffrey J. Figiel ‡, Igal Brener ‡§, Steven R. J. Brueck †, and George T. Wang *‡ † Center for High Technology Materials, University of New Mexico, 1313 Goddard Street SE, Albuquerque, New Mexico 87106, United States ‡ Sandia National Laboratories, Albuquerque, New Mexico 87185, United States § Center for Integrated Nanotechnology, Sandia National Laboratories, Albuquerque, New Mexico 87185, United States ∥ Institute of Photonics, Physics Department, University of Strathclyde, Wolfson Centre, 106 Rottenrow East, Glasgow, G4 0NW, United Kingdom ACS Photonics http://dx.doi.org/10.1021/acsphotonics.5b00039

Annular-shaped lasing emission is demonstrated from gallium nitride nanotubes fabricated using a two-step top-down technique. By optically pumping, we observe a clear threshold of 1055 kW/cm2, a narrow spectral linewidth of 0.19 nm, and guided emission from the nanotubes. Lasing is also demonstrated in a liquid environment, with an approximate doubling in threshold observed. The nanotube lasers could be of interest for optical nanofluidic applications or applications benefiting from a hollow beam shape. More generally, the results indicate that cross-sectional shape control can be employed to manipulate the properties of nanolasers.

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GROUP 3 - Power Electronics Group leader: Frédéric Morancho (LAAS-CNRS)

Information selected by Frédéric Morancho (LAAS-CNRS) and Yvon Cordier (CRHEA-CNRS)

Suppression of current leakage along mesa surfaces in GaN-based p-i-n diodes Zheng, B. ; Bo-Sheng ; Chen, P. ; Yu, C. ; Chang, Y. ; Ho, C. ; Wu, M. ; Hsieh, K. Institute of Electronic Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan. Electron Device Letters, IEEE http://dx.doi.org/10.1109/LED.2015.2458899

Trifluoromethane-containing plasma is used to passivate the mesa surfaces and suppress the surface leakage current of GaN p-i-n rectifiers. Reduction of surface leakage enhances the reverse blocking voltage by 25% measured at J???1 A/cm2. Differential forward resistances of control samples and plasma-treated ones are 0.65 mΩ-cm2 and 0.49 mΩ-cm2, respectively, and an excellent Baliga’s figure-of-merit of more than 800 MW/cm2, as compared to the conventional 545 MW/cm2, is achieved for GaN diodes fabricated on sapphire substrates. Wide bandgap (WBG) semiconductor power converters for DC microgrid applications Shenai, K. ; LoPel Corp., Naperville, IL, USA DC Microgrids (ICDCM), 2015 IEEE First International Conference on http://dx.doi.org/10.1109/ICDCM.2015.7152051

Important criteria for the widespread usage of DC electricity are the overall energy efficiency and cost of delivering electricity from the point of generation to the point of usage. Wide bandgap (WBG) semiconductor power switching devices, including those made from Silicon Carbide (SiC) and Gallium Nitride (GaN) semiconductors, offer unprecedented advantages over conventional silicon devices in terms of significantly increased energy efficiency and superior thermal performance. For example, for power conversion applications requiring power switches rated below 900V, commercial GaN lateral power transistors offer more than 5% higher energy efficiency with superior load regulation, especially for point-of-

load (PoL) converters and wireless energy transfer devices. For higher voltage applications, commercially available vertical SiC power diodes and MOSFETs provide increased energy efficiency than feasible with silicon power MOSFETs and IGBTs, especially for certain low- and medium-power inverters and DC-DC converters. Breakdown behaviour of high-voltage GaN-HEMTs W. Saito, T. Suwa, T. Uchihara, T. Naka, T. Kobayashi Toshiba Corp. Semiconductor & Storage Products Company, 1-1-1 Shibaura, Tokyo 105-8001, Japan Microelectronics Reliability http://dx.doi.org/10.1016/j.microrel.2015.06.126

The breakdown mechanism of high-voltage GaN-HEMT was analysed using the experimental I–V characteristics and two-dimensional device simulation results. The holes are generated by the impact ionization under high applied voltage. A part of the generated holes accumulates beneath the gate and lowers the gate potential barrier. As a result, the source leakage current flowing over the gate potential increases rapidly and breakdown occurs. From these results, suppression of the impact ionization and the hole remove structure are effective for a highly reliable design concerning the breakdown. Design and analysis of GaN FET-based resonant dc-dc converter Dong-Sik Kim ; Dong-Myoung Joo ; Byoung-Kuk Lee ; Jong-Soo Kim Div. of Electr., Electron. & Commun. Eng., Daejin Univ., Pocheon, South Korea Power Electronics and ECCE Asia (ICPE-ECCE Asia), 2015 9th International Conference on http://dx.doi.org/10.1109/ICPE.2015.7168196

This paper presents a design consideration of GaN FET-based resonant dc-dc converter, and the efficiency and ZVS characteristics of the resonant dc-dc converter based on GaN FET parameters are

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theoretically analyzed. To verify the validity of analysis, a 600W phase-shift full-bridge dc-dc converter is designed and implemented. The faulty turn-on and ZVS issue caused by GaN FET characteristics are analyzed and their improvement ideas are presented. Reliability studies of vertical GaN devices based on bulk GaN substrates Isik C. Kizilyallia, P. Bui-Quanga, D. Disneyb, H. Bhatiaa, Ozgur Aktasa a Avogy Inc., 677 River Oaks Parkway, San Jose, CA 95134, USA b Global Foundries, Santa Clara, CA 95054, USA Microelectronics Reliability http://dx.doi.org/10.1016/j.microrel.2015.07.012

There is great interest in wide band-gap semiconductor devices and most recently in vertical GaN structures for power electronic applications. In this paper initial reliability studies of vertical p–n diodes and vertical junction field effect transistors fabricated on pseudo bulk low defect density (104 to 106 cm− 2) GaN substrates are discussed. Homoepitaxial MOCVD growth of GaN on its native substrate and being able to control the doping in the drift layers in GaN has allowed the realization of vertical device architectures with drift layer thicknesses of 6 to 40 μm and net carrier electron concentrations of 2 × 1015 to 2 × 1016 cm− 3. This parameter range is suitable for applications requiring breakdown voltages of 1200 V to 5 kV with a proper edge termination strategy. Measured devices demonstrate power device figure of merit of differential specific on-resistance (Rsp) of 2.8 mΩ-cm2 for a breakdown voltage of 4.1 kV. The improvement in the substrate quality over the last few years has resulted in the fabrication of diodes with areas as large as 16 mm2, with breakdown voltages exceeding 1200 V, and pulsed (100 μs) currents of 100–400 A. Furthermore, impact ionization based avalanche breakdown has been demonstrated in GaN for the first time due to the high quality of the crystals grown on the native substrates. With these key demonstrations firmly in place, it is necessary to evaluate the reliability performance of vertical GaN devices on bulk GaN substrates. The results of high temperature reverse bias (HTRB), high temperature operating

life (HTOL), temperature humidity bias (THB), temperature cycling (TC), and inductive avalanche ruggedness tests conducted on vertical GaN devices packaged in standard power packages are reported. It is observed that fundamental failure mechanisms are almost always traced back to the starting substrate material quality, substrate miscut angle, and surface morphology post epi growth. No observation of Rds drift is made for vertical diodes or transistors fabricated on bulk GaN substrates under the stress conditions mentioned above once a suitable back metal and die attach process is developed. Avalanche Capability of Vertical GaN p-n Junctions on Bulk GaN Substrates Aktas, O. ; Kizilyalli, I.C. Avogy Inc., San Jose, CA 95134 USA Electron Device Letters, IEEE http://dx.doi.org/10.1109/LED.2015.2456914

Inductive avalanche test results presented in this letter demonstrate that GaN p-n diodes can sustain single-pulse and repetitive inductive avalanche currents. The 0.36 mm2 vertical GaN p-n diodes can sustain single-pulse avalanche currents as high as 10 A. The safe zone of the single pulse avalanche current is limited by peak pulse power and energy deposited in the device. The temperature dependent behavior of the breakdown voltage and the reverse-voltage at onset of avalanche has a positive temperature coefficient. Repetitive avalanche ruggedness testing was performed by applying 105 pulses at 5 kHz frequency with increasing repetitive stress current. Based on a population of 63 devices, the incremental failure rate under repetitive avalanche current increases with increasing avalanche current. The devices that survive the step stress test sustain no parametric drift under repetitive avalanche. Trapping induced parasitic effects in GaN-HEMT for power switching applications Meneghesso, G.Meneghini, M. ; Zanoni, E. ; Vanmeerbeek, P. ; Moens, P. Dept. of Inf. Eng., Univ. of Padova, Padua, Italy IC Design & Technology (ICICDT), 2015 International Conference on

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http://dx.doi.org/10.1109/ICICDT.2015.7165899

This paper summarizes our recent results on the analysis of the trapping-induced parasitic effects in GaN-based high electron mobility transistors for power switching applications. More specifically, we demonstrate the following relevant mechanisms: (i) dynamic Ron shows a significant increase when the devices are operated at high temperature levels; this effect is ascribed to a stronger trapping in the buffer region; (ii) the kinetics of buffer-related trapping processes can be effectively investigated by means of backgating tests, carried out at various temperature levels; (iii) buffer trapping is strongly correlated to drain-buffer vertical leakage. The reduction of vertical leakage is an important step towards the reduction of high temperature dynamic Ron. Finally, we demonstrate that by proper epitaxial design and device optimization it is possible to fabricate devices with very low dynamic Ron (measured at 150 °C, VDS=500 V). Analysis of GaN HEMT switching behavior Lautner, J. ; Piepenbreier, B. Electr. Drives & Machines, Univ. of Erlangen-Nuremberg, Erlangen, Germany ; Power Electronics and ECCE Asia (ICPE-ECCE Asia), 2015 9th International Conference on http://dx.doi.org/10.1109/ICPE.2015.7167840

This paper presents a comprehensive study of the GaN HEMT switching performance in a phase-leg configuration with special focus on the impact of different parasitic effects. Therefore, a simulation model of a double pulse test circuit with GaN devices and including parasitic elements is proposed. The causes of parasitic inductances and capacitances are discussed and their effects are analyzed. Furthermore, the influence of the gate resistance value and dead time is investigated. A double pulse tester was designed to experimentally verify the simulation results. This paper shows the switching transients of both devices in a phase-leg configuration for varying parameters graphically and offers a better insight into the switching behavior of GaN transistors. The understanding of the parasitic effects and varying parameter enables improved design and performance of fast switching power converters.

High breakdown voltage AlGaN/GaN HEMTs on free-standing GaN substrate Ng, J.H. Tone, K. ; Asubar, J.T. ; Tokuda, H. ; Kuzuhara, M. Grad. Sch. of Eng., Univ. of Fukui, Fukui, Japan Future of Electron Devices, Kansai (IMFEDK), 2015 IEEE International Meeting for http://dx.doi.org/10.1109/IMFEDK.2015.7158546

In this paper we have investigated the relationship between off-state breakdown voltage and gate-to-drain distance (Lgd) for AlGaN/GaN HEMTs fabricated on a free-standing GaN substrate. The off-state breakdown voltage exhibited a linear increase up to Lgd of around 80 μm but saturated at about 4000 V when Lgd > 80 μm. Therefore, we proposed that when Lgd <; 80 μm, the breakdown voltage of HEMTs was dominated by leakage current under the channel and when Lgd > 80 μm, it was determined by the leakage current outside of the channel. Commercialization and reliability of 600 V GaN power switches Kikkawa, T. Hosoda, T. ; Shono, K. ; Imanishi, K. ; Asai, Y. ; YiFeng Wu ; Likun Shen ; Smith, K. ; Dunn, D. ; Chowdhury, S. ; Smith, P. ; Gritters, J. ; McCarthy, L. ; Barr, R. ; Lal, R. ; Mishra, U. ; Parikh, P. Transphorm Japan, Inc., Aizu-Wakamatsu, Japan Reliability Physics Symposium (IRPS), 2015 IEEE International http://dx.doi.org/10.1109/IRPS.2015.7112766

The reliability of 600 V GaN power switches, fabricated in a silicon CMOS foundry, has been demonstrated. JEDEC qualification of cascode packages and the long term reliability of GaN power switches has been estimated for the first and shown to be greater than a million hours. Excellent switched/dynamic on-resistance up to 1000 V and breakdown voltage over 1500 V indicate the suitability of these devices for switching up to 480 V. Detailed data of high temperature reverse bias (HTRB) test is shown. High temperature DC stress test and high voltage off-state stress tests also corroborate the high reliability of these devices. This suite of initial, JEDEC & accelerated stress tests show that GaN-

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on-silicon power switches are ready for many commercial and industrial applications, would significantly reduce switching losses and system size and will impact all areas of electricity conversion, ranging from tablet chargers to photovoltaic inverters and electric vehicles. Modeling the effect of acceptor-type traps on internal electric field of a GaN-pin device phenomenon Chiu, Shao-Yen ; Tseng, Yu-Teng ; Yang, Wei-Chen ; Cheng, Keh-Yung Norman Episil Technologies Inc., Hsinchu, Taiwan ; Power Electronics and Drive Systems (PEDS), 2015 IEEE 11th International Conference on http://dx.doi.org/10.1109/PEDS.2015.7203577

The performance of a pin structure diode fabricated on epitaxial layer on a GaN template using re-growth p-type GaN technology by PAMBE. Experimental results show that relatively forward turn-on voltage and on-resistance are 3.1V and 5mΩ-cm2, respectively. Due to the metal-semiconductor interface has the lower p-ohmic contact. On the contrary, the breakdown voltage of the device operating greater than 800V is observed. Furthermore, the pin structure diode within acceptor-type traps using a two-dimensional simulator as GaN bulk within threading dislocations (about ∼108cm−2) was compared to including the electric field different from x and y position. It leads to substantially higher electric field as function of x position between the metal and the p-type GaN when drift layer is not fully depleted. Impact of gate insulator on the dc and dynamic performance of AlGaN/GaN MIS-HEMTs I. Rossettoa, M. Meneghinia, D. Bisia, A. Barbatoa, M. Van Hoveb, D. Marconb, T.-L. Wub, S. Decoutereb, G. Meneghessoa, E. Zanonia a Department of Information Engineering, University of Padova, Padova, Italy b Imec, Kapeldreef 75, B-3001 Leuven, Belgium Microelectronics Reliability http://dx.doi.org/10.1016/j.microrel.2015.06.130

This paper studies the impact of the properties of the SiN gate insulator on the dc and dynamic

performance of AlGaN/GaN Metal Insulator Semiconductor High Electron Mobility Transistors (MIS-HEMTs). We compare the dynamic and transient behaviour of devices with identical epitaxial structure and different gate insulators: RTCVD-SiN (rapid-thermal-chemical-vapour-deposition) and PEALD-SiN (plasma-enhanced-atomic-layer-deposition). We demonstrate the following important results: (i) the gate leakage of devices with PEALD-SiN insulator is three orders of magnitude lower than that of samples with RTCVD-SiN; (ii) the use of PEALD-SiN reduces significantly the transistor threshold voltage hysteresis; (iii) both sets of samples show measurable threshold voltage shift when submitted to forward gate bias. In addition we demonstrate (iv) that the VTH shift is well correlated with the gate forward leakage and bias, for both sets of samples. This result indicates that trapping is induced by the injection of electrons in the gate insulator when a positive bias is applied to the gate; in PEALD SiN devices, the reduction of the gate (forward) leakage results in a significant decrease in VTH shift. Experimental study of Single Event Effects induced by heavy ion irradiation in enhancement mode GaN power HEMT C. Abbatea, G. Busattoa, F. Iannuzzoa, S. Mattiazzob, A. Sanseverinoa, L. Silvestrinb, D. Tedescoa, F. Velardia a Dipartimento di Ingegneria Elettrica e dell'Informazione, Università degli Studi di Cassino e del Lazio Meridionale, Cassino, Italy b Dipartimento di Fisica e di Astronomia “Galileo Galilei”, Università degli Studi di Padova, Padova, Italy Microelectronics Reliability http://dx.doi.org/10.1016/j.microrel.2015.06.139

An experimental characterization of the behavior of GaN power HEMTs during heavy ion irradiation is presented. It is demonstrated that normally off GaN power HEMTs are affected by a significant charge amplification mechanism. These devices are subjected to damages implying relevant increases of the drain leakage current. The damages are permanent and cumulative and depend on the biasing conditions. Higher voltage devices rated at 100 V and 200 V suffer from Single Event Burnouts which take place at biasing voltages lower than the maximum rated one.

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Forward Bias Gate Breakdown Mechanism in Enhancement-mode p-GaN gate AlGaN/GaN High-electron-mobility Transistors (HEMTs) Wu, T. Marcon, D. ; You, S. ; Posthuma, N.E. ; Bakeroot, B. ; Stoffels, S. ; Van Hove, M. ; Groeseneken, G. ; Decoutere, S. Imec, Kapeldreef 75, Leuven, Belgium. Electron Device Letters, IEEE http://dx.doi.org/10.1109/LED.2015.2465137

In this work, we studied the forward bias gate breakdown mechanism on Enhancement-mode p-GaN gate AlGaN/GaN HEMTs. To the best of our knowledge, it is the first time that the temperature dependency of the forward gate breakdown has been characterized. We report for the first time on the observation of a positive temperature dependency, i. e., a higher temperature leads to a higher gate breakdown voltage. Such unexpected behavior is explained by avalanche breakdown mechanism: at a high positive gate bias, electron/hole pairs are generated in the depletion region at the Schottky metal/p-GaN junction. Furthermore, at a high gate bias but before the catastrophic gate breakdown, a light emission was detected by a emission microscopy measurement (EMMI). This effect indicates an avalanche luminescence, which is mainly due to the recombination of the generated electron/hole pairs. AlGaN/GaN heterojunction field-effect transistor with embedded clamping diode Sang-Woo Han, Sung-Hoon Park and Ho-Young Cha School of Electronic and Electrical Engineering, Hongik University, Seoul 121-791, Republic of Korea Applied Physics Express Vol. 8; 081001 http://dx.doi.org/10.7567/APEX.8.081001

We developed an AlGaN/GaN heterojunction field-effect transistor with a MOS gate and an embedded clamping diode to achieve normally-off operation. The input signal level shifts downward when a capacitor is connected to the device because of the embedded diode, which mimics a clamping circuit. Thus, the device, which initially has a negative threshold voltage, functions as a normally-off device with a ""virtual"" positive

threshold voltage. The proposed device has the advantages of high current density and easy implementation compared with the conventional AlGaN/GaN-based normally-off devices. Thermal analysis and improvement of cascode GaN device package for totem-pole bridgeless PFC rectifier Shuojie Shea, Wenli Zhangb, Zhengyang Liub, Fred C. Leeb, Xiucheng Huangb, Weijing Dub, Qiang Lib a College of Electronic Information and Control Engineering, Beijing University of Technology, 100 Ping Le Yuan, Chaoyang District, Beijing 100124, China b Center for Power Electronics Systems, Bradley Department of Electrical and Computer Engineering, Virginia Tech, 669 Whittemore Hall, 1185 Perry Street, Blacksburg, VA 24061, USA Applied Thermal Engineering Volume 90, 5 November 2015, Pages 413–423 http://dx.doi.org/10.1016/j.applthermaleng.2015.06.094

The totem-pole bridgeless power factor correction (PFC) rectifier has a simpler topology and higher efficiency than other boost-type bridgeless PFC rectifiers. Its promising performance is enabled by using high-voltage gallium nitride (GaN) high-electron-mobility transistors, which have considerably better figures of merit (e.g., lower reverse recovery charges and less switching losses) than the state-of-the-art silicon metal-oxide-semiconductor field-effect transistors. Cascode GaN devices in traditional packages, i.e., the TO-220 and power quad flat no-lead, are used in the totem-pole PFC boost rectifier. But the parasitic inductances induced by the traditional packages not only significantly deteriorate the switching characteristics of the discrete GaN device but also adversely affect the performance of the built PFC rectifier. A new stack-die packaging structure with an embedded capacitor has been introduced and proven to be efficient in reducing parasitic ringing at the turn-off transition and achieving true zero-voltage-switching turn-on. However, the thermal dissipation capability of the device packaged in this configuration becomes a limitation on further pushing the operating frequency and the output current level for high-efficiency power conversion. This paper focuses on the thermal analysis of the cascode GaN

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devices in different packages and the GaN-based multichip module used in a two-phase totem-pole bridgeless PFC boost rectifier. A series of thermal models are built based on the actual structures and materials of the packaged devices to evaluate their thermal performance. Finite element analysis (FEA) simulation results of the cascode GaN device in a flip-chip format demonstrate the possibility of increasing the device switching speed while maintaining the peak temperature of the device below 125 °C. Thermal analysis of the GaN-based power module in a very similar structure is also conducted using the FEA method. Experimental data measured using the fabricated devices and modules validate the simulation results. The developed new package in a flip-chip configuration enhances the thermal dissipation capability of the cascode GaN device in the stack-die format. The GaN-based power module built using the same packaging structure also demonstrates desirable thermal performance. Threshold voltage controlled by gate area and gate recess in inverted trapezoidal trigate AlGaN/GaN MOS high-electron-mobility transistors with photoenhanced chemical and plasma-enhanced atomic layer deposition oxides Po-Chun Yeh1, Yun-Wei Lin3, Yue-Lin Huang3, Jui-Hung Hung1, Bo-Ren Lin1, Lucas Yang1, Cheng-Han Wu2, Tzu-Kuan Wu2, Chao-Hsin Wu1,2 and Lung-Han Peng1 1 Department of Electrical Engineering and Institute of Photonics and Optoelectronics, National Taiwan University, Taipei 10617, Taiwan, R.O.C. 2 Department of Electrical Engineering and Graduate Institute of Electronics Engineering, National Taiwan University, Taipei 10617, Taiwan, R.O.C. 3 Department of Physics, National Dong Hwa University, Hualien 974, Taiwan, R.O.C. Applied Physics Express Vol. 8; 084101 http://dx.doi.org/10.7567/APEX.8.084101

An enhancement-mode AlGaN/GaN inverted-trapezoid trigate MOS high-electron-mobility transistor (HEMT), featuring double-layer oxides formed by photoenhanced chemical oxidation and plasma-enhanced atomic layer deposition (PEALD) oxide deposition, was shown to support the threshold voltage (Vth) with linear slopes of 0.36 V/nm and −0.32 V/µm2 scaled with recess depth

and device area, respectively. The proposed device exhibited Vth of 1.2 V, current on/off ratio of 108, and fT/fmax of 9/36 GHz at a gate length/width of 250/360 nm. These observations can be ascribed to the combined effects of (a) an interfacial negative space charge of 3.2 µC/cm2 in the gate-recessed device that partially compensates for the spontaneous charge and (b) side-wall passivation that preserves the high-mobility channel. Extensive Investigation of Time-Dependent Breakdown of GaN-HEMTs Submitted to OFF-State Stress Meneghini, M. ; Rossetto, I. ; Hurkx, F. ; Sonsky, J. ; Croon, J.A. ; Meneghesso, G. ; Zanoni, E. Dept. of Inf. Eng., Univ. of Padua, Padua, Italy Electron Devices, IEEE Transactions on Volume:62 , Issue: 8, Page(s):2549 - 2554 http://dx.doi.org/10.1109/TED.2015.2446032

This paper reports the experimental demonstration of time-dependent dielectric breakdown in GaN-based high-electron mobility transistors (HEMTs) submitted to OFF-state stress. Based on combined breakdown measurements, constant voltage stress tests, and 2-D simulations, we demonstrate the following relevant results. First, GaN-based HEMTs with a breakdown voltage higher than 1000 V (evaluated by dc measurements) may show time-dependent failure when exposed to OFF-state stress with VDS in the range 600-700 V. Second, time-to-failure (TTF) is Weibull-distributed, and has an exponential dependence on the stress voltage level. Third, time-dependent breakdown is ascribed to the failure of the SiN dielectric at the edge of the gate overhang, on the drain side. Fourth, 2-D simulations confirm that-in this region-the electric field exceeds 6 MV/cm, i.e., the dielectric strength of SiN. Finally, we demonstrate that by limiting the electric field in the nitride through epitaxy and process improvements, it is possible to increase the TTF by three orders of magnitude.

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Surface state of GaN after rapid-thermal-annealing using AlN cap-layer G. El-Zammar a, W. Khalfaoui a, T. Oheix a, b, A. Yvon b, E. Collard b, F. Cayrel a, D. Alquier a a Université François Rabelais, Tours, GREMAN, CNRS UMR 7347, 10 rue Thalès de Milet CS 97155, 37071 Tours Cedex 2, France b STMicroelectronics, 10 rue Thalès de Milet CS 97155, 37071 Tours Cedex 2, France Applied Surface Science Volume 355, 15 November 2015, Pages 1044–1050 http://dx.doi.org/10.1016/j.apsusc.2015.07.201

Critical issues need to be overcome to produce high performance Schottky diodes on gallium nitride (GaN). To activate dopant, high temperature thermal treatments are required but damage GaN surface where hexagonal pits appear and prevent any device processing. In this paper, we investigated the efficiency of cap-layers on GaN during thermal treatments to avoid degradation. Aluminum nitride (AlN) and silicon oxide (SiOx) were grown on GaN by direct current reactive magnetron sputtering and plasma-enhanced chemical vapor deposition, respectively. AlN growth parameters were studied to understand their effect on the grown layers and their protection efficiency. Focused ion beam was used to measure AlN layer thickness. Crystalline quality and exact composition were verified using X-ray diffraction and energy dispersive X-ray spectroscopy. Two types of rapid thermal annealing at high temperatures were investigated. Surface roughness and pits density were evaluated using atomic force microscopy and scanning electron microscopy. Cap-layers wet etching was processed in H3PO4 at 120 °C for AlN and in HF (10%) for SiOx. This work reveals effective protection of GaN during thermal treatments at temperatures as high as 1150 °C. Low surface roughness was obtained. Furthermore, no hexagonal pit was observed on the surface.

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GROUP 4 - Advanced Electronics and RF Group leader: Jean-Claude Dejaeger (IEMN)

Information selected by Jean-Claude Dejaeger (IEMN) and Yvon Cordier (CRHEA-CNRS)

High performance AlGaN/GaN HEMTs with AlN/SiNx passivation

Tan Xin (谭鑫)1, Lü Yuanjie (吕元杰)1, Gu Guodong

(顾国栋)1, Wang Li (王丽)2, Dun Shaobo (敦少博)1,

Song Xubo (宋旭波)1, Guo Hongyu (郭红雨)1, Yin

Jiayun (尹甲运)1, Cai Shujun (蔡树军)1 and Feng

Zhihong (冯志红)1

1 National Key Laboratory of Application Specific Integrated Circuit (ASIC), Hebei Semiconductor Research Institute, Shijiazhuang 050051, China 2 China National Defense Sciences Technology Information Center, Beijing 100040, China Journal of Semiconductors Vol. 36; 074008 http://dx.doi.org/10.1088/1674-4926/36/7/074008

AlGaN/GaN high electron-mobility transistors (HEMTs) with 5 nm AlN passivation by plasma enhanced atomic layer deposition (PEALD) were fabricated, covered by 50 nm SiNx which was grown by plasma enhanced chemical vapor deposition (PECVD). With PEALD AlN passivation, current collapse was suppressed more effectively and the devices show better subthreshold characteristics. Moreover, the insertion of AlN increased the RF transconductance, which lead to a higher cut-off frequency. Temperature dependence of DC characteristics demonstrated that the degradations of drain current and maximum transconductance at elevated temperatures for the AlN/SiNx passivated devices were much smaller compared with the devices with SiNx passivation, indicating that PEALD AlN passivation can improve the high temperature operation of the AlGaN/GaN HEMTs. Enhanced sheet carrier densities in polarization controlled AlInN/AlN/GaN/InGaN field-effect transistor on Si (111) J. Hennig1,a), A. Dadgar1, H. Witte1, J. Bläsing1, A. Lesnik1, A. Strittmatter1 and A. Krost1 1 Otto-von-Guericke-Universität Magdeburg, Universitätsplatz 2, 39106 Magdeburg, Germany

AIP Advances Vol. 5, 077146 (2015); http://dx.doi.org/10.1063/1.4927402

We report on GaN based field-effect transistor (FET) structures exhibiting sheet carrier densities of n = 2.9 1013 cm−2 for high-power transistor applications. By grading the indium-content of InGaN layers grown prior to a conventional GaN/AlN/AlInN FET structure control of the channel width at the GaN/AlN interface is obtained. The composition of the InGaN layer was graded from nominally xIn = 30 % to pure GaN just below the AlN/AlInN interface. Simulations reveal the impact of the additional InGaN layer on the potential well width which controls the sheet carrier density within the channel region of the devices. Benchmarking the InxGa1−xN/GaN/AlN/Al0.87In0.13N based FETs against GaN/AlN/AlInN FET reference structures we found increased maximum current densities of ISD = 1300 mA/mm (560 mA/mm). In addition, the InGaN layer helps to achieve broader transconductance profiles as well as reduced leakage currents. Impact of residual carbon impurities and gallium vacancies on trapping effects in AlGaN/GaN metal insulator semiconductor high electron mobility transistors Martin Huber1,2, Marco Silvestri1, Lauri Knuuttila1, Gianmauro Pozzovivo1, Andrei Andreev1, Andrey Kadashchuk3,4, Alberta Bonanni2 and Anders Lundskog1 1 Infineon Technologies Austria AG, Siemensstrasse 2, A-9500 Villach, Austria 2 Institute of Semiconductor and Solid State Physics, Johannes Kepler University, Altenbergerstrasse 69, A-4040 Linz, Austria 3 IMEC, Kapeldreef 75, B-3001 Leuven, Belgium 4 Institute of Physics, National Academy of Science of Ukraine, Prospekt Nauki 46, 03028 Kyiv, Ukraine Applied Physics Letters Vol. 107, 032106 (2015); http://dx.doi.org/10.1063/1.4927405

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Effects of residual C impurities and Ga vacancies on the dynamic instabilities of AlN/AlGaN/GaN metal insulator semiconductor high electron mobility transistors are investigated. Secondary ion mass spectroscopy, positron annihilation spectroscopy, and steady state and time-resolved photoluminescence (PL) measurements have been performed in conjunction with electrical characterization and current transient analyses. The correlation between yellow luminescence (YL), C- and Ga vacancy concentrations is investigated. Time-resolved PL indicating the CN ON complex as the main source of the YL, while Ga vacancies or related complexes with C seem not to play a major role. The device dynamic performance is found to be significantly dependent on the C concentration close to the channel of the transistor. Additionally, the magnitude of the YL is found to be in agreement with the threshold voltage shift and with the on-resistance degradation. Trap analysis of the GaN buffer shows an apparent activation energy of ∼0.8 eV for all samples, pointing to a common dominating trapping process and that the growth parameters affect solely the density of trap centres. It is inferred that the trapping process is likely to be directly related to C based defects. Low thermal resistance of a GaN-on-SiC transistor structure with improved structural properties at the interface Jr-Tai Chen a, James W. Pomeroy c, Niklas Rorsman b, Chao Xia a, Chariya Virojanadara a, Urban Forsberg a, Martin Kuball c, Erik Janzén a a Department of Physics, Chemistry, and Biology (IFM), Linköping University, SE 581 83 Linköping, Sweden b Microwave Electronics Laboratory, MC2, Chalmers University of Technology, SE-412 96 Göteborg, Sweden c Center for Device Thermography and Reliability, H.H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, UK Journal of Crystal Growth Volume 428, 15 October 2015, Pages 54–58 http://dx.doi.org/10.1016/j.jcrysgro.2015.07.021

The crystalline quality of AlGaN/GaN heterostructures was improved by optimization of surface pretreatment of the SiC substrate in a hot-wall metal-organic chemical vapor deposition reactor. X-ray photoelectron spectroscopy

measurements revealed that oxygen- and carbon-related contaminants were still present on the SiC surface treated at 1200 °C in H2 ambience, which hinders growth of thin AlN nucleation layers with high crystalline quality. As the H2 pretreatment temperature increased to 1240 °C, the crystalline quality of the 105 nm thick AlN nucleation layers in the studied series reached an optimal value in terms of full width at half-maximum of the rocking curves of the (002) and (105) peaks of 64 and 447 arcsec, respectively. The improvement of the AlN growth also consequently facilitated a growth of the GaN buffer layers with high crystalline quality. The rocking curves of the GaN (002) and (102) peaks were thus improved from 209 and 276 arcsec to 149 and 194 arcsec, respectively. In addition to a correlation between the thermal resistance and the structural quality of an AlN nucleation layer, we found that the microstructural disorder of the SiC surface and the morphological defects of the AlN nucleation layers to be responsible for a substantial thermal resistance. Moreover, in order to decrease the thermal resistance in the GaN/SiC interfacial region, the thickness of the AlN nucleation layer was then reduced to 35 nm, which was shown sufficient to grow AlGaN/GaN heterostructures with high crystalline quality. Finally, with the 35 nm thick high-quality AlN nucleation layer a record low thermal boundary resistance of 1.3×10−8 m2 K/W, measured at an elevated temperature of 160 °C, in a GaN-on-SiC transistor structure was achieved. Ultrathin barrier AlN/GaN high electron mobility transistors grown at a dramatically reduced growth temperature by pulsed metal organic chemical vapor deposition JunShuai Xue1,a), JinCheng Zhang1,b) and Yue Hao1 1 Key Laboratory of Wide Band Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi'an 710071, People's Republic of China Applied Physics Letters Vol. 107, 043503 (2015) http://dx.doi.org/10.1063/1.4927743

Ultrathin-barrier AlN/GaN heterostructures were grown on sapphire substrates by pulsed metal organic chemical vapor deposition (PMOCVD)

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using indium as a surfactant at a dramatically reduced growth temperature of 830 °C. Upon optimization of growth parameters, an electron mobility of 1398 cm2/V s together with a two-dimensional-electron-gas density of 1.3 × 1013 cm−2 was obtained for a 4 nm thick AlN barrier. The grown structures featured well-ordered parallel atomic steps with a root-mean-square roughness of 0.15 nm in a 5 × 5 μm2 area revealed by atomic-force-microscopic image. Finally, the potential of such structures for device application was demonstrated by fabricating and testing under dc operation AlN/GaN high-electron-mobility transistors. These results indicate that this low temperature PMOCVD growth technique is promising for the fabrication of GaN-based electronic devices. Ti/Al Based Ohmic Contact to As-Grown N-Polar GaN Feng Zhi-Hong (???)1, Wang Xian-Bin (???)1,2, Wang Li (??)3, Lv Yuan-Jie (???)1, Fang Yu-Long (???)1, Dun Shao-Bo (???)1 and Zhao Zheng-Ping (???)1,2 1 National Key Laboratory of Application Specific Integrated Circuit (ASIC), Hebei Semiconductor Research Institute, Shijiazhuang 050051 2 School of Information Engineering, Hebei University of Technology, Tianjin 300019 3 Information Center of Science and Technology, Beijing 100085 Chinese Physics Letters Vol. 32 087102 http://dx.doi.org/10.1088/0256-307X/32/8/087102

Ti/Al based Ohmic contacts to as-grown N-polar GaN are investigated by cross-section transmission electron microscopy and energy dispersive x-ray spectroscopy. Due to the higher oxygen background doping in the N-polar GaN, the Al metal in Ohmic stacks is found to react with background oxygen more easily, resulting in more AlOx. In addition, the formation of AlOx is affected by the Al layer thickness greatly. The AlOx combined with the presence of AlN is detrimental to the Ohmic contacts for N-polar GaN compared with Ga-polar GaN. With the reduction of the Al layer thickness to some extent, less AlOx and AlN are formed, and lower Ohmic contact resistance is obtained. The lowest contact resistivity ? of 1.97 ×

10?6 ?centerdotcm2 is achieved with the Al layer thickness of 80 nm. Trap states in enhancement-mode double heterostructures AlGaN/GaN high electron mobility transistors with different GaN channel layer thicknesses Yunlong He1, Peixian Li2,a), Chong Wang1,b), Xiangdong Li1, Shenglei Zhao1, Minhan Mi1, Jiuqing Pei1, Jincheng Zhang1, Xiaohua Ma1,2 and Yue Hao1,c) 1 Key Laboratory of Wide Band Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi'an 710071, People's Republic of China 2 School of Advanced Materials and Nanotechnology, Xidian University, Xi'an 710071, People's Republic of China Applied Physics Letters Vol. 107, 063501 (2015) http://dx.doi.org/10.1063/1.4928477

This is the report on trap states in enhancement-mode AlGaN/GaN/AlGaN double heterostructures high electron mobility transistors by fluorine plasma treatment with different GaN channel layer thicknesses. Compared with the thick GaN channel layer sample, the thin one has smaller 2DEG concentration, lower electron mobility, lower saturation current, and lower peak transconductance, but it has a higher threshold voltage of 1.2 V. Deep level transient spectroscopy measurements are used to obtain the accurate capture cross section of trap states. By frequency dependent capacitance and conductance measurements, the trap state density of (1.98–2.56) × 1012 cm−2 eV−1 is located at ET in a range of (0.37–0.44) eV in the thin sample, while the trap state density of (2.3–2.92) × 1012 cm−2 eV−1 is located at ET in a range of (0.33–0.38) eV in the thick one. It indicates that the trap states in the thin sample are deeper than those in the thick one. High-Efficiency, High-Temperature Continuous Class-E Sub-Waveform Solution AlGaN/GaN Power Amplifier Carrubba, V. ; Maroldt, S. ; Musser, M. ; Ture, E. ; Dammann, M. ; van Raay, F. ; Quay, R. ; Bruckner, P. ; Ambacher, O. IAF Fraunhofer Institute for Applied Solid State Physics, Freiburg, Germany

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Microwave and Wireless Components Letters, IEEE Volume:25, Issue: 8, Page(s): 526 - 528 http://dx.doi.org/10.1109/LMWC.2015.2440758

This letter presents the realization of a high-efficiency, high-temperature Continuous Class-E Sub-Waveform Solution power amplifier using for the first time GaN technology. The recently introduced Continuous Class-E PA mode theory has revealed new and various impedance solutions for which high efficiency switch mode PAs can be realized. The investigation carried out in this work clearly shows that very high efficiency is still delivered despite the smaller voltage waveform peak when compared to standard Class-E, leading to more reliable PAs. The Continuous Class-E Sub-Waveform Solution PA prototype shows efficiency as high as 80% while delivering output power of 4 W and gain {>} 10 dB at 2 GHz of frequency and ambient temperature. The PA module has also been tested at high temperature {\rm T}=150^{\circ} C revealing targeted performance with efficiency up to 71% while delivering 3.5 W of output power. Reliability measurements also show satisfactory results in the time frame up to 1500 hours. Scattering induced by Al segregation in AlGaN/GaN heterostructures Xiwen Liu,1 Dong Ji,2 and Yanwu Lu1,a) 1Department of Physics, Beijing Jiaotong University, Beijing 100044, People’s Republic of China 2School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona 85281, USA Applied Physics Letters Vol. 107, 072105 (2015); http://dx.doi.org/10.1063/1.4928932

The effect of Al segregation near dislocations on the mobility of two-dimensional electron gas in AlGaN/GaN heterostructure-based high-electron-mobility transistors was investigated. Exponentially varied composition fluctuation was effective in describing Al segregation near dislocations when calculating scattering behavior. Mobility, which was limited by Al segregation surrounding dislocation lines, was calculated to be in the order of 103 cm2/Vs to 106 cm2/Vs. Results indicated that the mobility in AlGaN/GaN

heterojunction was enhanced upon the reduction of dislocation density at low temperature. This study contributes to generating higher electron mobility in AlGaN/GaN heterojunctions. Investigation of the dynamic on-state resistance of AlGaN/GaN HEMTs M. Rzin a, N. Labat a, N. Malbert a, A. Curutchet a, L. Brunel b, B. Lambert b a IMS Laboratory, University of Bordeaux, 351 Cours de la libération, Talence, France b United Monolithic Semiconductor, 10 Avenue du Québec, 91140 Villebon-sur-Yvette, France Microelectronics Reliability http://dx.doi.org/10.1016/j.microrel.2015.07.001

The dynamic on-state resistance (RON) increase in AlGaN/GaN high-electron-mobility transistors (HEMTs) has been investigated by pulsed I–V measurements on devices issued from UMS GaN technology. We have studied the influence of the measurement setup on the pulsed I–V measurements and highlighted the importance of the IDS(t) waveforms to verify the validity of the measurements. The RON is not sensitive to short time transients below 10 μs as well as for fresh and HTRB aged devices. The dynamic resistance (RON) is doubled in off-state conditions by increasing VDS0 from 0 V to 50 V. The threshold voltage VTH of aged devices has not shifted during the HTRB aging test carried out for 2200 h. Therefore, trapping effects responsible for the increase of RON are rather more located in the gate-source and drain–source access regions than under the gate. Correlation between transient evolutions of the gate and drain currents in AlGaN/GaN technologies O. Lazăr a, J.G. Tartarin a, B. Lambert b, C. Moreau c, J.L. Roux d a CNRS-LAAS (UPS), 31031 Toulouse, France b UMS, 91140 Villebon-sur-Yvette, France c DGA-MI, 35998 Rennes Armées, France d CNES, 31400 Toulouse, France Microelectronics Reliability http://dx.doi.org/10.1016/j.microrel.2015.06.122

This work focuses on short term and long term time evolution of charges in the context of early

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identification of failure mechanisms in AlGaN/GaN High Electron Mobility Transistors (HEMTs). High power and high frequency devices are needed for new microwave applications, and large band-gap HEMTs offer a powerful alternative to traditional technologies (Si, GaAs, SiGe etc.); however, reliability issues still hamper the potential of these technologies to push their limits in terms of mean time to failure or junction temperature. This paper contributes to the investigation of transient behaviors of gate and drain currents over a large time scale for gallium nitride HEMTs; a correlation is found between the currents' evolution, in spite of the non-monotonic behavior, and a model is given through a mathematical relationship. Charges under the gated zone of the transistor are found to evolve with time, and turn into command variations of the electron density in the 2DEG. This work addresses the consequences of charge dependent mechanisms on the drain current's drop, and thus of the output power. First demonstration of GaN-based vertical nanowire FET with top-down approach Jo, Young-Woo; Son, Dong-Hyeok ; Lee, Dong-Gi ; Won, Chul-Ho ; Seo, Jae Hwa ; Kang, In Man ; Lee, Jung-Hee School of electronics engineering, Kyungpook National University, Daegu 702-701, Korea Device Research Conference (DRC), 2015 73rd Annual http://dx.doi.org/10.1109/DRC.2015.7175539

GaN-based field effect transistors (FETs) are widely used in power switching and amplifier application due to its superior material properties such as wide band-gap energy, high breakdown field, and high electron saturation velocity, which results in high output current and high breakdown voltage [1]. On the other hand, nanowire transistors are extensively investigated to improve device performance such as fin-shaped FETs (FinFETs), lateral and vertical type nanowire FETs [2 – 4]. Especially, vertical nanowire FETs (VNFETs) are currently being evaluated as a promising device technology due to its negligible trapping and leakage from the buffer layer, wrap-gated structure and possibility of very short gate length (below 20 nm). VNFETs using Si, InAs and InGaAs materials were already introduced. However, GaN-based VNFETs have been never fabricated

due to difficulty in obtaining vertical nanowire structure with high aspect ratio and their complex fabrication process. In this work, we fabricated the GaN-based VNFET, for the first time, by combining conventional e-beam lithography and dry etching technique with strong anisotropic TMAH wet etching. Gan-on-diamond wafers: Recent developments Ejeckam, F. Francis, D. ; Faili, F. ; Lowe, F. ; Twitchen, D. ; Bolliger, B. Element Six Technol., US Corp., Santa Clara, CA, USA Semiconductor Technology International Conference (CSTIC), 2015 China http://dx.doi.org/10.1109/CSTIC.2015.7153472

In this work, we discuss the state-of-the-art of GaN-on-diamond wafer technology at Element Six. We report our recent demonstration of 100mm (4") GaN-on-diamond HEMT epitaxial wafers-with the highest thermal conductivity of diamond (>1500 W/mK) yet. The wafers exhibit <;20μm bow mounted on-carrier, sheet resistivity of <;450 Ohms/sq, and CV specs that are in-line with industry expectations. Two-stage high-efficiency X-Band GaN MMIC PA/ rectifier Coffey, M. ; Schafer, S. ; Popovic, Z. Electr. Comput. & Energy Eng., Univ. of Colorado at Boulder, Boulder, CO, USA Microwave Symposium (IMS), 2015 IEEE MTT-S International http://dx.doi.org/10.1109/MWSYM.2015.7166979

This paper details the performance of an X-Band MMIC fabricated in a 0.15 μm GaN on SiC process that operates as both a high-efficiency power amplifier (PA) and a high-efficiency rectifier. The MMIC characterized as a PA biased in class AB, achieves over 10W of output power, >20 dB of gain and a PAE of 50% at 9.9 GHz. As a rectifier, the MMIC, achieves over 52% RF-DC conversion efficiency at a power level of >8W. To the best of the authors' knowledge, this is the first demonstration of a two-stage power combined high-efficiency GaN X-band MMIC power rectifier. The applications are in bi-directional high power wireless energy transfer.

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Nitride devices prepared on flexible substrates Fujioka, Hiroshi ; Ueno, K. ; Kobayashi, A. ; Ohta, Jituo Institute of Industrial Science, the University of Tokyo, 4-6-1 Komaba, Meguro-ku, 153-8505, Japan Active-Matrix Flatpanel Displays and Devices (AM-FPD), 2015 22nd International Workshop on http://dx.doi.org/10.1109/AM-FPD.2015.7173192

In this presentation, we will demonstrate successful operation of nitride devices prepared on various low cost substrates by the use of a newly developed low temperature epitaxial growth technique named pulsed sputtering deposition (PSD). We have found that performances of GaN devices such as LEDs or HEMTs fabricated with PSD are as good as those fabricated with conventional MOCVD. We have also found that the use of PSD low temperature epitaxial growth technique allows us to utilize chemically vulnerable materials that have never been used as substrates for GaN based devices. These results indicate that the low growth temperature PSD epitaxial process is quite advantageous for fabrication of nitride devices on various flexible substrates. GaN-MMIC Doherty power amplifier with integrated reconfigurable input network for microwave backhaul applications Giofre, R. Piazzon, L. ; Colantonio, P. ; Giannini, F. ; Camarchia, V. ; Quaglia, R. ; Pirola, M. ; Ramella, C Univ. of Roma Tor Vergata, Rome, Italy Microwave Symposium (IMS), 2015 IEEE MTT-S International http://dx.doi.org/10.1109/MWSYM.2015.7166763

A 7 GHz GaN MMIC Doherty power amplifier with reconfigurable input network for backhaul applications, is presented. The reconfigurable solution is conceived to be simply implemented in MMIC technologies. To demonstrate the effectiveness of the strategy, a second Doherty with fixed input network, has been designed for comparison. Both prototypes have been realized adopting a commercial GaN HEMT process and characterized in large signal conditions. The experimental results prove the capability of the proposed solution to overcome the issues related to the inaccuracy of the active device nonlinear

models especially for the Class-C bias condition required by the Peak amplifier. At 7 GHz both MMICs exhibit an output power of 40 dBm. However, at 6 dB of output power backoff, the reconfigurable Doherty efficiency is 43%, 10% higher than the one of the DPA with fixed input network. The evolution of transistors for power amplifiers: 1947 to today Niehenke, E.C. Niehenke Consulting, Baltimore, MD, USA Microwave Symposium (IMS), 2015 IEEE MTT-S International http://dx.doi.org/10.1109/MWSYM.2015.7166768

This paper traces the development of transistors for power amplifiers (PAs). Technological transistor innovations have raised output power levels, the frequency of operation and the efficiency of power amplifiers. Devices to be discussed include the bipolar junction transistor (BJT), heterojunction bipolar transistor (HBT), complimentary metal oxide semiconductor (CMOS), laterally diffused metal oxide semiconductor (LDMOS), metal-semiconductor field effect transistor (MESFET), high electron mobility transistor (HEMT), and pseudomorphic high electron transistor (PHEMT). Semiconductors for PAs include Silicon (Si), Gallium Arsenide (GaAs), Indium Phosphide (InP), and Gallium Nitride (GaN) and the various heterojunctions of these semiconductors. X-band wireless power transfer with two-stage high-efficiency GaN PA/ rectifier Schafer, S. ; Coffey, M. ; Popovic, Z. Electr. Comput. & Energy Eng., Univ. of Colorado at Boulder, Boulder, CO, USA ; Wireless Power Transfer Conference (WPTC), 2015 IEEE http://dx.doi.org/10.1109/WPT.2015.7140186

A 2-stage X-band GaN MMIC operating as a power amplifier and rectifier is measured in a wireless power transfer link. The PA operates at 9.9 GHz in class-AB and achieves 10W of output power and >20 dB of gain. As a rectifier, the MMIC achieves over 52% RF-DC conversion efficiency at a power level of >8W. In a wireless powering link at a

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distance of 5 cm, the system achieves 10% DC-DC efficiency. The applications are bi-directional high power directional wireless power transfer (WPT). Over 65% PAE GaN voltage-mode class d power amplifier for 465 MHz operation using bootstrap drive Nakamizo, H. Mukai, K. ; Shinjo, S. ; Gheidi, H. ; Asbeck, P. Mitsubishi Electr. Corp., Kamakura, Japan Power Amplifiers for Wireless and Radio Applications (PAWR), 2015 IEEE Topical Conference on http://dx.doi.org/10.1109/PAWR.2015.7139202

We report a digitally-driven switching-mode amplifier using GaN devices in Voltage-Mode Class D operation, for use at 465 MHz (the recently designated frequency for LTE Band 31). The amplifier is fabricated as an integrated circuit including output devices and drivers. The output circuit employs two stacked GaN FETs; a bootstrap-drive configuration is used in order to increase the driver-stage efficiency for the uppermost GaN FET. The GaN VMCD amplifier achieves peak power-added efficiency of 66.6%, and an output power of 3.3W. At 6dB power backoff, power-added efficiency of 36.3% is achieved. These power-added efficiency values are the highest for reported GaN VMCD amplifiers at a commercial wireless frequency. Full-Wave Modeling of THz RTD-Gated GaN HEMTs Sai N. Tenneti, Niru K. Nahar, John L. Volakis ElectroScience Laboratory, Electrical and Computer Engineering Dept., The Ohio State University, 1330 Kinnear Road, Columbus OH, 43212, USA Infrared Physics & Technology http://dx.doi.org/10.1016/j.infrared.2015.07.017

Modeling transistors at terahertz frequencies is challenging, because electromagnetic and quantum effects that are negligible in lower frequencies become limiting factors in device performance. Though previous work has focused on modeling the channel of a high-electron mobility transistor (HEMT) using hydrodynamic equations, a more complete toolset is needed to describe submillimeter-wave device gain

performance. This paper introduces a simulator that couples full-wave Maxwell’s equations with Schrodinger-based charge transport equations, and is used to evaluate the gain performance of a GaN HEMT at THz. This novel simulator is also used to evaluate the effect on gain when a resonant tunneling diode (RTD) is integrated with a HEMT. Upon validation with published work, we state the feasibility of RTD-gated GaN HEMT structures that have resonances up to 2.3 THz and gain up to 6 dB. An athermal measurement technique for long time constants traps characterization in GaN HEMT transistors A. Divay a, M. Masmoudi a, O. Latry a, ,C. Duperrier b, F. Temcamani c a Normandie Université, University of Rouen, GPM UMR CNRS 6634, 76300 Saint Etienne du Rouvray, France b University of Cergy, ETIS UMR 8051 CNRS, ENSEA, 95000 Cergy-Pontoise, France c ECS-Lab, ENSEA, 95000 Cergy-Pontoise, France Microelectronics Reliability http://dx.doi.org/10.1016/j.microrel.2015.06.074

GaN High Electron Mobility Transistors (HEMTs) are very promising for high power switching and radiofrequency operation. However, the lack of reliability feedback is one of its major drawbacks. Trapping effect especially is one of the main performance limitations of such components. Many measurement techniques exist for trapping effects characterization, especially for short time constant traps (μs to several ms). However for longer time constants, self-heating may distort the measurements. This paper presents an electrical and athermal transient measurement method which has been developed to study the trapping and detrapping time constants of such components. It allows the extraction of slow transients without self-heating problems and is usable in long term electrical stress experiments. A simulation of this method with a simplified component's model and the measurements results are presented. With this technique, we investigated especially the long time constants (τ > 20 ms) over a range of temperature from 10 °C to 105 °C. We observed three thermally activated trap signatures on GaN devices with our method.

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An automatized time-domain set-up for on-wafer charaterization, doherty oriented, of high power GaN HEMTS Ayari, L. ; Ayad, M. ; Byk, E. ; Camiade, M. ; Neveux, G. ; Barataud, D. XLIM, Univ. of Limoges, Limoges, France Microwave Measurement Conference (ARFTG), 2015 85th http://dx.doi.org/10.1109/ARFTG.2015.7162905

This paper presents an automatized on-wafer time-domain active load-pull set-up specifically developed for the characterization of High Power GaN High-Electron Mobility Transistors (HEMTs). This set-up is associated to a specific methodology for the design of Doherty Power Amplifier (DPA). This methodology has been applied to a GaN technology transistor: from the on-wafer measured Time-Domain Waveforms (TDW) acquisition, all data required for the design of a Doherty power amplifier are directly extracted. Designers have the direct knowledge of the optimal characteristics of high power transistors along the output back-off (OBO) at fundamental frequency and also the maximum obtainable operating bandwidth of the final desired Doherty PA. Microfluidically reconfigurable GaN power amplifier on multilayer organic substrate for s-band and c-band applications Chlieh, O.L. ; Khan, W.T. ; Papapolymerou, J. Sch. of Electr. & Comput. Eng., Georgia Inst. of Technol., Atlanta, GA, USA Microwave Symposium (IMS), 2015 IEEE MTT-S International http://dx.doi.org/10.1109/MWSYM.2015.7167140

This paper presents, for the first time, a microfluidic tuning solution on a multilayer organic substrate to tune the frequency response of a GaN-based power amplifier (PA) from 2.4 GHz to 5.8 GHz and vice versa. By changing the fluid inside the matching networks microchannels, the packaged PA large signal response can be tuned allowing it to work optimally at the two specified frequencies based on the fluid in use. In this work,

the fluids used are acetone and air and are meant to work for 2.4 GHz and 5.8 GHz respectively. The measured large signal data for the PA shows that Pout = 35.02 dBm, PAE = 36.41 % for Pin = 21 dBm at 2.3 GHz (acetone configuration) and Pout = 36.88 dBm, PAE = 44.03 % for Pin = 25 dBm at 5.7 GHz (air configuration). These numbers improve significantly for higher input power levels.

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GANEX | Newsletter No. 31-32 - III-N Technology 29

GROUP 5 - Sensors and MEMS Group leader: Marc Faucher (IEMN) Information selected by Knowmade

Thermo-acoustic engineering of silicon microresonators via evanescent waves R. Tabrizian1,a) and F. Ayazi2 1 Electrical Engineering and Computer Science Department, University of Michigan, Ann Arbor, Michigan 48109, USA 2 School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30308, USA Applied Physics Letters Vol.106, 263504 (2015); http://dx.doi.org/10.1063/1.4923056

A temperature-compensated silicon micromechanical resonator with a quadratic temperature characteristic is realized by acoustic engineering. Energy-trapped resonance modes are synthesized by acoustic coupling of propagating and evanescent extensional waves in waveguides with rectangular cross section. Highly different temperature sensitivity of propagating and evanescent waves is used to engineer the linear temperature coefficient of frequency. The resulted quadratic temperature characteristic has a well-defined turn-over temperature that can be tailored by relative energy distribution between propagating and evanescent acoustic fields. A 76 MHz prototype is implemented in single crystal silicon. Two high quality factor and closely spaced resonance modes, created from efficient energy trapping of extensional waves, are excited through thin aluminum nitride film. Having different evanescent wave constituents and energy distribution across the device, these modes show different turn over points of 67 °C and 87 °C for their quadratic temperature characteristic. Low-Dimensional Structure Vacuum-Ultraviolet-Sensitive (λ < 200 nm) Photodetector with Fast-Response Speed Based on High-Quality AlN Micro/Nanowire Wei Zheng, Feng Huang, Ruisheng Zheng and Honglei Wu

1 State Key Laboratory of Optoelectronic Materials and Technologies, School of Physics and Engineering, Sun Yat-Sen University, Guangzhou, P. R. China 2 Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Institute of Optoelectronics, Shenzhen University, Shenzhen, P. R. China Advanced Materials Volume 27, Issue 26, July 8, 2015, Page: 3971, http://dx.doi.org/10.1002/adma.201570176

A vacuum-ultraviolet (VUV) (10–200 nm) low-dimensional photodetector is fabricated by F. Huang and co-workers, as described on page 3921. A two-step physical vapor-transport method is designed to grow high-quality single-crystal aluminum nitride micro-/nanowires, and realize a relatively fast response speed for VUV detection. This work may open a way for developing diminutive, power-saving, and low-cost VUV materials and sensors integrated on satellites and aerospace-planes. Characterisation of multi roof tile-shaped out-of-plane vibrational modes in aluminium-nitride-actuated self-sensing micro-resonators in liquid media Martin Kucera1,2,a), Elisabeth Wistrela1, Georg Pfusterschmied1, Víctor Ruiz-Díez3, José Luis Sánchez-Rojas3, Johannes Schalko1, Achim Bittner1 and Ulrich Schmid1 1 Institute of Sensor and Actuator Systems, Vienna University of Technology, Floragasse 7, 1040 Vienna, Austria 2 Austrian Centre of Competence for Tribology, AC2T research GmbH, Viktor-Kaplan-Straße 2, 2700 Wr. Neustadt, Austria 3 Group of Microsystems, Actuators and Sensors, E.T.S.I. Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain Applied Physics Letters Vol. 107, 053506 (2015); http://dx.doi.org/10.1063/1.4928429

This letter reports on higher orders of an advanced out-of-plane bending mode in

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aluminium-nitride (AlN)-actuated cantilever plates achieving the highest quality factors (Q-factor) of cantilever-based MEMS (micro electromechanical system) resonators in liquids up to now. Devices based on a 20 μm thick silicon cantilever were fabricated and characterised by optical and electrical measurements in air and in different liquids. Furthermore, finite element method eigenmode analyses were performed, showing an excellent agreement with the measured mode shape and the electrical characteristics. The highest Q-factor was achieved in deionised water with Q = 366, operated at the 10th order mode at a resonance frequency less than 4 MHz. This is the highest value ever measured in liquid media with a cantilever-based MEMS resonator up to now and exceeds the Q-factors of state of the art resonators in liquids in the given resonance frequency range by a factor of about 4. Furthermore, the strain related conductance peak of the multi roof tile-shaped modes is superior, showing great potential for further electrode design optimisation. Compared to common out-of-plane bending modes, this combination of most beneficial properties is unique, making this type of vibration mode the first choice for a large variety of resonator-based liquid-phase sensing applications. Piezotransistive transduction of femtoscale displacement for photoacoustic spectroscopy Abdul Talukdar, M. Faheem Khan, Dongkyu Lee, Seonghwan Kim, Thomas Thundat & Goutam Koley Department of Electrical Engineering, University of South Carolina, Columbia, South Carolina 29208, USA Department of Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta T6G 2V4, Canada Department of Mechanical and Manufacturing Engineering, University of Calgary, Calgary, Alberta T2N 1N4, Canada Department of Electrical Engineering, Clemson University, Clemson, South Carolina 29634, USA Nature Communications Vol. 6, Article number: 7885 http://dx.doi.org/10.1038/ncomms8885

Measurement of femtoscale displacements in the ultrasonic frequency range is attractive for advanced material characterization and sensing,

yet major challenges remain in their reliable transduction using non-optical modalities, which can dramatically reduce the size and complexity of the transducer assembly. Here we demonstrate femtoscale displacement transduction using an AlGaN/GaN heterojunction field effect transistor-integrated GaN microcantilever that utilizes piezoelectric polarization-induced changes in two-dimensional electron gas to transduce displacement with very high sensitivity. The piezotransistor demonstrated an ultra-high gauge factor of 8,700 while consuming an extremely low power of 1.36 nW, and transduced external excitation with a superior noise-limited resolution of 12.43 fm Hz−1/2 and an outstanding responsivity of 170 nV fm−1, which is comparable to the optical transduction limits. These extraordinary characteristics, which enabled unique detection of nanogram quantity of analytes using photoacoustic spectroscopy, can be readily exploited in realizing a multitude of novel sensing paradigms. Piezoelectric nonlinearity in GaN Lamb mode resonators Wang, Siping ; Popa, Laura C. ; Weinstein, Dana Massachusetts Institute of Technology, Cambridge, USA ; Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS), 2015 Transducers - 2015 18th International Conference on http://dx.doi.org/10.1109/TRANSDUCERS.2015.7181091

This paper reports on the measurement of nonlinearity in GaN Lamb mode resonators

subjected to power levels between ᄒ10 and +10 dBm. In these devices, nonlinearity manifests itself as both frequency shift (Δ/f of 60–128 ppm) and change in motional impedance (ΔRm/Rm of 13–33%). In this work, we decouple the contributions from self-heating and strain-induced piezoelectric nonlinearity to ΔRm/Rm, and conclude that strain-induced change in piezoelectric coefficients Δe31 and Δe33 is the dominant cause of ΔRm/Rm, accounting for 31% of the total 33% observed shift. The result is consistent with 2nd order nonlinear coefficients previously derived analytically [1].

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A comprehensive study of material and structural designs of bulk acoustic resonator (BAR) filters for wireless applications Pao, J.J. ; Kyi, W. ; Riaziat, M. ; Huo, Y. OEpic Semicond. Inc., Sunnyvale, CA, USA ; Wireless Symposium (IWS), 2015 IEEE International http://dx.doi.org/10.1109/IEEE-IWS.2015.7164555

A study of a solidly mounted bulk acoustic wave resonator (SMR) filter is presented. An overall design and fabrication summary is described, with both materials and structures of the resonator devices considered. Aluminum Nitride (AlN) is utilized as the piezoelectric material to convert electromagnetic signals to acoustic waves. Molybdenum (Mo) is used as the electrode material. A distributed Bragg reflector (DBR) stack of alternating Tungsten (W) and Silicon Dioxide (SiO2) is embedded. Basic device fabrication process steps are presented, and measured filter responses are compared with simulated filter responses. III–V nitride microcantilever as a displacement sensor Talukdar, Abdul ; Koley, Goutam University of South Carolina, Columbia, USA ; Solid-State Sensors, Actuators and Microsystems (TRANSDUCERS), 2015 Transducers - 2015 18th International Conference on http://dx.doi.org/10.1109/TRANSDUCERS.2015.7180891

The application of gated piezoresitor (or ‘piezotransistor’) embedded GaN microcantilever utilizing unique properties of AlGaN/GaN Heterojunction Field Effect Transistor (HFET) to very significantly enhance the device performance in order to transduce femtoscale displacement have been demonstrated. This novel technology offers several orders higher sensitivity than state-of-the-art and enabled detection of minute explosive in open ambient by photoacoustic spectroscopy. Asymmetrically and Vertically-Coupled Hybrid Si/GaN Microring Resonators for On-Chip Optical Interconnects Thubthimthong, B. ; Sasaki, T. ; Hane, K.

Department of Nanomechanics, Graduate School of Engineering, Tohoku University, 6-6-1 Aoba, Aramaki, Aoba, Sendai, Miyagi, 980-8579 Japan. Photonics Journal, IEEE http://dx.doi.org/10.1109/JPHOT.2015.2464721

A working small-footprint asymmetrically and vertically-coupled hybrid Si/GaN microring resonator (HMR) was demonstrated. The HMR of a minimum radius of 20 m was fabricated in a high-yield (90%) hybrid nanophotonic platform that allowed interactions between the GaN microring and the underlying Si waveguide circuit. The HMR’s spectral response across telecommunication Cand L-bands was measured. The high extinction ratio of up to 17 dB, the resonance linewidth as narrow as 40 pm, and the intrinsic quality factor of up to 70,000, which was the highest value for GaN microring reported so far, were achieved. The explicit analytical model for the high-index-contrast HMR was developed. Our basic study opened new possibilities for exploring GaN-Si non-linear phenomena and for developing complex on-chip optical interconnects. Unique detection of organic vapors below their auto-ignition temperature using III-V Nitride based triangular microcantilever heater Ifat Jahangir a, Ehtesham Bin Quddus b, Goutam Koley c a Department of Electrical Engineering, University of South Carolina, Columbia, SC 29208, USA b Intel Corporation, Portland, Oregon, 97208, USA c Department of Electrical and Computer Engineering, Clemson University, Clemson, SC 29634, USA Sensors and Actuators B: Chemical http://dx.doi.org/10.1016/j.snb.2015.08.059

We report on the unique detection of dilute volatile organic compounds below their auto-ignition temperature using a novel AlGaN/GaN heterostructure based triangular microcantilever heater. With a low input power of 12 mW, the microcantilever heater was found to reach a maximum temperature of 330 °C at the tip, which was verified through infrared microscopy and Raman spectroscopy. Unique threshold voltages were observed for various organic analytes with different functional groups, beyond which the

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heater current started to increase sharply in presence of analytes, which correlated strongly with their latent heat of evaporation. Dilute vapors with concentrations as low as 50 parts per million (ppm) could be detected selectively with a noise limited resolution down to 5 ppm. On the other hand, the magnitude of change of current for a fixed applied voltage was found to be dependent on the molecular dipole moment of the analytes, which can likely be attributed to the strong surface polarization of AlGaN. A simple circuit model has been proposed to explain the observations. Heat transfer and Joule heating simulations were performed using finite element method to model the electro-thermal characteristics of the microcantilever heater, which were in good agreement with the experimental observations.

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GROUP 6 - Photovoltaics and Energy harvesting Group leader: Eva Monroy (INAC-CEA)

Information selected by Knowmade

Modeling of polarization charge in N-face InGaN/GaN MQW solar cells R. Belghouthi a, S. Taamalli a, b, F. Echouchene a, H. Mejri a, H. Belmabrouk a a Laboratoire d’Electronique ET de Microélectronique, Département de physique, Faculté des Sciences de Monastir, 5019, Tunisia b Laboratoire de Photonique d’anger, E.a. 4464, Université d’anger, 2Bd Lavoisier, 49045 Angers Cedex 01, France Materials Science in Semiconductor Processing Volume 40, December 2015, Pages 424–428 http://dx.doi.org/10.1016/j.mssp.2015.07.009

The present work reports on a theoretical study of spontaneous and piezoelectric polarization effects on the photovoltaic characteristics of InGaN/GaN multiple quantum well solar cells. More especially, it will prove that the use of heterostructures with N-face as a surface polarity can further improve the photovoltaic conversion. A new model including piezoelectric polarization is developed. In this paper, a part of simulation is also paid to analyze the dependence of the photocurrent density, the open circuit voltage, the output power and the efficiency versus the In composition and the number of quantum well units. As has been found, a maximum of energy conversion is expected to achieve 19 percent for optimum alloy composition. An attempt to explain the photovoltaic behavior of the solar cells in correlation of obtained results will be attempted. Surface passivation of crystalline silicon by sputtered AlOx/AlNx stacks toward low-cost high-efficiency silicon solar cells Hyunju Lee1,4, Keigo Ueda2, Yuya Enomoto2, Koji Arafune2,4, Haruhiko Yoshida2,4, Shin-ichi Satoh2,4, Toyohiro Chikyow3 and Atsushi Ogura1,4 1 School of Science and Technology, Meiji University, Kawasaki 214-8571, Japan 2 Graduate School of Engineering, University of Hyogo, Himeji, Hyogo 671-2280, Japan 3 National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan

4 Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012, Japan Japanese Journal of Applied Physics Vol; 54 08KD18 http://dx.doi.org/10.7567/JJAP.54.08KD18

Recently, excellent surface passivation has been achieved for both p- and n-type silicon solar cells using AlOx/SiNx:H stacks deposited by atomic layer deposition and plasma-enhanced chemical vapor deposition. However, alternative materials and deposition methods could provide practical options for large-scale manufacturing of commercial solar cells. In this study we demonstrate that AlOx/AlNx stacks fabricated by reactive radio-frequency magnetron sputtering can provide fairly good surface passivation (Smax of ~30 cm/s) regardless of AlOx thickness, which is found to be due to the high negative fixed charge density (Qeff of −2.8 × 1012 cm−2) and moderately low interface trap density (Dit of 2.0 × 1011 eV−1centerdotcm−2). The stacks also show fairly good antireflection performance in the visible and near-infrared spectral region. The demonstrated surface passivation and antireflection performance of in situ reactively sputtered AlOx/AlNx stacks make them a promising candidate for a surface-passivating antireflection coating on silicon solar cells. MOVPE growth of thick (~1 µm) InGaN on AlN/Si substrates for InGaN/Si tandem solar cells Akio Yamamoto1,2, Kazuki Kodama1, Md. Tanvir Hasan1,2, Naoteru Shigekawa3 and Masaaki Kuzuhara1 1 University of Fukui, Fukui 910-8507, Japan 2 JST-CREST, Chiyoda, Tokyo 102-0076, Japan 3 Osaka City University, Osaka 558-8585, Japan Japanese Journal of Applied Physics Vol. 54 08KA12 http://dx.doi.org/10.7567/JJAP.54.08KA12

"In order to develop key technologies for InGaN/Si two-junction tandem solar cells, MOVPE growth of thick InGaN on Si p-on-n cell structures has

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been studied. By clarifying the phase separation behavior of MOVPE InGaN, a thick (~1 µm) InxGa1−xN (x ~ 0.5) without phase separation is successfully grown on AlN/Si(111) wafers. A sufficient current flow for the operation of the tandem cell is obtained through n-InGaN/AlN/p-Si structures by employing the annealing of AlN/Si wafer at around 1000 °C in NH3 flow just before InGaN growth. The annealing of AlN/Si wafers also brings about the degradation of the underlying Si pn junction. The optimization of the annealing conditions is required to balance such favorable and unfavorable effects. InxGa1?xN/GaN Multiple Quantum Well Solar Cells with Conversion Efficiency of 3.77% Liu Shi-Ming 1, Xiao Hong-Ling 1, Wang Quan )1,2, Yan Jun-Da 1, Zhan Xiang-Mi 1, Gong Jia-Min 2, Wang Xiao-Liang 1,3 and Wang Zhan-Guo 1,3 1 Key Lab of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, P. O. Box 912, Beijing 100083 2 School of Electronic Engineering, Xi'an University of Posts and Telecommunications, Xi'an 710121 3 Beijing Key Laboratory of Low-Dimensional Semiconductor Materials and Devices, P. O. Box 912, Beijing 100083 Chinese Physics Letters Vol. 32 088401 http://dx.doi.org/10.1088/0256-307X/32/8/088401

We report on fabrication and photovoltaic characteristics of InxGa1?xN/GaN multiple quantum well solar cells with different indium compositions and barrier thicknesses. The as-grown samples are characterized by high-resolution x-ray diffraction and reciprocal space mapping. The results show that the sample with a thick barrier thickness (10.0nm) and high indium composition (0.23) has better crystalline quality. In addition, the dark current density-voltage (J?V) measurement of this device shows a significant decrease of leakage current, which leads to high open-circuit voltage Voc. Through the J?V characteristics under an Air Mass 1.5 Global (AM 1.5 G) illumination, this device exhibits a Voc of 1.89 V, a short-circuit current density Jsc of 3.92 mA/cm2 and a fill factor of 50.96%. As a result, the conversion efficiency (?) is enhanced to be 3.77% in comparison with other devices.

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GROUP 7 - Materials, Technology and Fundamental Group leader: Jean-Christophe Harmand (LPN-CNRS)

NANO

Information selected by Knowmade

Core–shell InGaN/GaN nanowire light emitting diodes analyzed by electron beam induced current microscopy and cathodoluminescence mapping M. Tchernycheva,*a V. Neplokh,a H. Zhang,a P. Lavenus,a L. Rigutti,ab F. Bayle,a F. H. Julien,a A. Babichev,acd G. Jacopin,e L. Largeau,f R. Ciechonski,g G. Vescovig and O. Krylioukh A Institut d'Electronique Fondamentale, UMR 8622 CNRS, University Paris Sud, 91405 Orsay cedex, France E-mail: maria.tchernycheva@u-psud.fr b Groupe de Physique des Matériaux, UMR CNRS 6634, University and INSA of Rouen, Normandie University, 76800 St. Etienne du Rouvray, France c ITMO University, 197101 St. Petersburg, Russia d Ioffe Institute, 194021 St. Petersburg, Russia e ICMP LOEQ Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland f LPN-CNRS, Route de Nozay, 91460 Marcoussis, France g GLO AB, Ideon Science Park, Scheelevägen 17, S-223 70 Lund, Sweden h GLO-USA, 1225 Bordeaux Dr, Sunnyvale, USA Nanoscale 2015,7, 11692-11701 http://dx.doi.org/10.1039/C5NR00623F

We report on the electron beam induced current (EBIC) microscopy and cathodoluminescence (CL) characterization correlated with compositional analysis of light emitting diodes based on core/shell InGaN/GaN nanowire arrays. The EBIC mapping of cleaved fully operational devices allows to probe the electrical properties of the active region with a nanoscale resolution. In particular, the electrical activity of the p–n junction on the m-planes and on the semi-polar planes of individual nanowires is assessed in top view and cross-sectional geometries. The EBIC maps combined with CL characterization demonstrate the impact of the compositional gradients along the wire axis on the electrical and optical signals: the reduction of the EBIC signal toward the nanowire top is accompanied by an increase of the CL intensity. This effect is

interpreted as a consequence of the In and Al gradients in the quantum well and in the electron blocking layer, which influence the carrier extraction efficiency. The interface between the nanowire core and the radially grown layer is shown to produce in some cases a transitory EBIC signal. This observation is explained by the presence of charged traps at this interface, which can be saturated by electron irradiation. GaN nanowires with pentagon shape cross-section by ammonia-source molecular beam epitaxy Yong Lin, Benjamin Leung, Qiming Li, Jeffrey. J. Figiel, George T. Wang Sandia National Laboratories, Albuquerque, New Mexico 87185, United States Journal of Crystal Growth Volume 427, 1 October 2015, Pages 67–71 http://dx.doi.org/10.1016/j.jcrysgro.2015.07.006

Ammonia-based molecular beam epitaxy (NH3-MBE) was used to grow catalyst-assisted GaN nanowires on View the MathML source(11¯02) r-plane sapphire substrates. Dislocation free View the MathML source[112¯0] oriented nanowires are formed with pentagon shape cross-section, instead of the usual triangular shape facet configuration. Specifically, the cross-section is the result of the additional two nonpolar View the MathML source{101¯0} side facets, which appear due to a decrease in relative growth rate of the View the MathML source{101¯0} facets to the View the MathML source{101¯1} and View the MathML source{101¯1} facets under the growth regime in NH3-MBE. Compared to GaN nanowires grown by Ni-catalyzed metal–organic chemical vapor deposition, the NH3-MBE grown GaN nanowires show more than an order of magnitude increase in band-edge to yellow luminescence intensity ratio, as measured by cathodoluminescence, indicating improved microstructural and optical properties.

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Design and comparative study of lateral and vertical LEDs with graphene as current spreading layer Shivani Palakurthya, b, c, Sumitra Singha, b, Suchandan Pala, b, Chenna Dhanavantria, b a CSIR-Network of Institutes for Solar Energy (CSIR-NISE), Pilani 333031, Rajasthan, India b Opto-electronic Devices Group, CSIR – Central Electronics Engineering Research Institute (CSIR-CEERI), Pilani 333031, Rajasthan, India c Birla Institute of Technology and Science, Pilani-Hyderabad Campus, India Superlattices and Microstructures Volume 86, October 2015, Pages 86–94 http://dx.doi.org/10.1016/j.spmi.2015.07.029

This study analyzes the current spreading effect of graphene on lateral and vertical light emitting diodes (LEDs). We observe an improvement in uniformity of current distribution, light output power and wall-plug efficiency in lateral LEDs (L-LEDs) with graphene current spreading layer (CSL) as compared to those with indium tin oxide (ITO) CSL. From the results we conclude that graphene CSL may be better alternative to ITO CSL. We further carried out a comparative study of lateral and vertical LEDs with graphene CSL. We observe 17% higher light output power, 16% higher wall-plug efficiency and 62% lower series resistance in the case of V-LEDs with graphene CSL when compared to that of L-LEDs with a graphene CSL. Reasons behind these results have been discussed. Formation of GaN quantum dots by molecular beam epitaxy using NH3 as nitrogen source B. Damilano1,a), J. Brault1 and J. Massies1 1 CRHEA-CNRS, Centre de Recherche sur l'Hétéro-Epitaxie et ses Applications, Centre National de la Recherche Scientifique, Rue B. Grégory, Valbonne 06560, France Journal of Applied Physics Vol. 118, 024304 (2015); http://dx.doi.org/10.1063/1.4923425

Self-assembled GaN quantum dots (QDs) in AlxGa1−xN (0.3 ≤ x ≤ 1) were grown on c-plane sapphire and Si (111) substrates by molecular beam epitaxy using ammonia as nitrogen source. The QD formation temperature was varied from

650 °C to 800 °C. Surprisingly, the density and size of QDs formed in this temperature range are very similar. This has been explained by considering together experimental results obtained from reflection high-energy electron diffraction, atomic force microscopy, and photoluminescence to discuss the interplay between thermodynamics and kinetics in the QD formation mechanisms. Finally, possible ways to better control the QD optical properties are proposed Structural and electronic properties of GaN nanowires with embedded In x Ga1− x N nanodisks J. Kioseoglou1,a), Th. Pavloudis1, Th. Kehagias1, Ph. Komninou1, Th. Karakostas1, C. D. Latham2, M. J. Rayson2, P. R. Briddon3 and M. Eickhoff4 1 Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece 2 Department of Chemistry, University of Surrey, Guildford, Surrey GU2 7XH, United Kingdom 3 School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom 4 Institute of Experimental Physics I, Justus-Liebig-University Giessen, D-35392 Giessen, Germany Journal of Applied Physics Vol. 118, 034301 (2015); http://dx.doi.org/10.1063/1.4926757

In the present study, the effects of various types of strain and indium concentration on the total energy and optoelectronic properties of GaN nanowires (NWs) with embedded In x Ga1− x N nanodisks (NDs) are examined. In particular, the bi-axial, hydrostatic, and uniaxial strain states of the embedded In x Ga1− x N NDs are investigated for multiple In concentrations. Density functional theory is employed to calculate the band structure of the NWs. The theoretical analysis finds that the supercell-size-dependent characteristics calculated for our 972-atom NW models are very close to the infinite supercell-size limit. It is established that the embedded In x Ga1− x N NDs do not induce deep states in the band gap of the NWs. A bowing parameter of 1.82 eV is derived from our analysis in the quadratic Vegard's formula for the band gaps at the various In concentrations of the investigated In x Ga1− x N NDs in GaN NW structures. It is

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concluded that up to ∼10% of In, the hydrostatic strain state is competitive with the bi-axial due to the radial absorption of the strain on the surfaces. Above this value, the dominant strain state is the bi-axial one. Thus, hydrostatic and bi-axial strain components coexist in the embedded NDs, and they are of different physical origin. The bi-axial strain comes from growth on lattice mismatched substrates, while the hydrostatic strain originates from the lateral relaxation of the surfaces. Double superstructures in InGaN/GaN nano-pyramid arrays Chiao-Yun Chang a, Heng Li a, Kuo-Bin Hong a, Ya-Yu Yang b, Wei-Chih Lai b, Tien-Chang Lu a a Department of Photonics & Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 300, Taiwan b Department of Photonic, National Cheng Kung University, Tainan 700, Taiwan Superlattices and Microstructures Volume 86, October 2015, Pages 275–279 http://dx.doi.org/10.1016/j.spmi.2015.07.059

We have fabricated and investigated InGaN/GaN nanopyramid arrays grown on c-plane sapphire by selective area growth technique. The double InGaN/GaN superstructures were formed in one GaN pyramid observed in transmittance emission microscopy. The two growth faces on GaN nanopyramind showed different growth rates, resulted in double superheterostructures of semi-polar facets for InGaN/GaN multiple quantum wells (MQWs) and c-plane InGaN/GaN nano-hetero-disk (NHD) under the nanoscale growth condition. The c-plane InGaN/GaN NHD had high Indium composition due to the pulling effect, exhibiting double wavelength emissions from GaN nanopyramid. And InGaN/GaN MQWs and c-plane InGaN/GaN NHD showed extremely low quantum confinement Stark effect, yielding great light emission efficiency. This result is beneficial for the development of blue, green and white light-emitting diodes.

Inclined angle-controlled growth of GaN nanorods on m-sapphire by metal organic chemical vapor deposition without a catalyst Kyuseung Lee1, Sooryong Chae1, Jongjin Jang1, Daehong Min1, Jaehwan Kim1, Daeyong Eom1, Yang-Seok Yoo2, Yong-Hoon Cho2 and Okhyun Nam1 1 Convergence Center for Advanced Nano Semiconductor (CANS), Department of Nano-Optical Engineering, Korea Polytechnic University (KPU), Siheung 429-793, Korea 2 Department of Physics, KAIST Center for LED Research, and KI for the NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Korea Nanotechnology Vol. 26; 335601 http://dx.doi.org/10.1088/0957-4484/26/33/335601

"In this study, we have intentionally grown novel types of (11-22)- and (1-10-3)-oriented3 and self-assembled inclined GaN nanorods (NRs) on (10-10) m-sapphire substrates using metal organic chemical vapor deposition without catalysts and ex situ patterning. Nitridation of the m-sapphire surface was observed to be crucial to the inclined angle as well as the growth direction of the GaN NRs. Polarity-selective KOH etching confirmed that both (11-22) and (1-10-3) GaN NRs are nitrogen-polar. Using pole figure measurements and selective area electron diffraction patterns, the epitaxial relationship between the inclined (11-22) and (1-10-3) GaN NRs and m-sapphire substrates was systematically demonstrated. Furthermore, it was verified that the GaN NRs were single-crystalline wurtzite structures. We observed that stacking fault-related defects were generated during the initial growth stage using high-resolution transmission electron microscopy. The blue-shift of the near band edge (NBE) peak in the inclined angle-controlled GaN NRs can be explained by a band filling effect through carrier saturation of the conduction band, resulting from a high Si-doping concentration; in addition, the decay time of NBE emission in (11-22)- and (1-10-3)-oriented NRs was much shorter than that of stacking fault-related emission. These results suggest that defect-free inclined GaN NRs can be grown on m-sapphire without ex situ treatment.

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Attribution of the 3.45 eV GaN nanowires luminescence to inversion domain boundaries Thomas Auzelle1,a), Benedikt Haas2, Martien Den Hertog3, Jean-Luc Rouvière2, Bruno Daudin1 and Bruno Gayral1 1 Université Grenoble Alpes, CEA-CNRS, NPSC, F-38054 Grenoble, France 2 Université Grenoble Alpes, CEA-INAC/UJF-Grenoble1, SP2M, LEMMA, F-38054 Grenoble, France 3 Université Grenoble Alpes, CNRS, Institut Néel, F-38042 Grenoble, France Applied Physics Letters Vol. 107, 051904 (2015); http://dx.doi.org/10.1063/1.4927826

"Using correlated experiments on single nanowires (NWs) by microphotoluminescence (μ-PL) and high resolution scanning transmission electron microscopy, we attribute the 3.45 eV luminescence of GaN NWs grown by plasma assisted molecular beam epitaxy (PA-MBE) to the presence of prismatic inversion domain boundaries (pIDBs). This attribution is further strengthened by a recent publication demonstrating the observation of pIDBs in PA-MBE grown GaN NWs. A statistical study of the presence of 3.45 eV lines in NWs PL spectra allows to estimate the ratio of single NWs nucleating with a pIDB to be 50% in the sample under scrutiny. Interplay of strain and indium incorporation in InGaN/GaN dot-in-a-wire nanostructures by scanning transmission electron microscopy Focus on Chemical Imaging Steffi Y Woo1,2, Nicolas Gauquelin1,2,4, Hieu P T Nguyen3,5, Zetian Mi3 and Gianluigi A Botton1,2 1 Department of Materials Science and Engineering, McMaster University, Hamilton, ON L8S 4L7, Canada 2 Brockhouse Institute for Materials Research and Canadian Centre for Electron Microscopy, McMaster University, Hamilton, ON L8S 4M1, Canada 3 Department of Electrical & Computer Engineering, McGill University, Montreal, QC H3A 0E9, Canada 4 Current address: EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerpen, Belgium 5 Current address: Department of Electrical and Computer Engineering, New Jersey Institute of Technology, University Heights, Newark, NJ 07102, USA Nanotechnology Vol. 26; 344002

http://dx.doi.org/10.1088/0957-4484/26/34/344002

The interplay between strain and composition is at the basis of heterostructure design to engineer new properties. The influence of the strain distribution on the incorporation of indium during the formation of multiple InGaN/GaN quantum dots (QDs) in nanowire (NW) heterostructures has been investigated, using the combined techniques of geometric phase analysis of atomic-resolution images and quantitative elemental mapping from core-loss electron energy-loss spectroscopy within scanning transmission electron microscopy. The variation in In-content between successive QDs within individual NWs shows a dependence on the magnitude of compressive strain along the growth direction within the underlying GaN barrier layer, which affects the incorporation of In-atoms to minimize the local effective strain energy. Observations suggest that the interfacial misfit between InGaN/GaN within the embedded QDs is mitigated by strain partitioning into both materials, and results in normal stresses inflicted by the presence of the surrounding GaN shell. These experimental measurements are linked to the local piezoelectric polarization fields for individual QDs, and are discussed in terms of the photoluminescence from an ensemble of NWs. Stacking fault related luminescence in GaN nanorods M Forsberg1, A Serban1, I Poenaru2, C-L Hsiao1, M Junaid3, J Birch1 and G Pozina1 1 Department of Physics, Chemistry, and Biology (IFM), Link?ping University, S-581 83 Link?ping, Sweden 2 Fraunhofer ISC, Project Group Materials Recycling and Resource Strategy IWKS, 63457 Hanau, Germany 3 RWTH Aachen University, Kopernikusstr. 10, D-52074 Aachen, Germany Nanotechnology Vol. 26 355203 http://dx.doi.org/10.1088/0957-4484/26/35/355203

Optical and structural properties are presented for GaN nanorods (NRs) grown in the [0001] direction on Si(111) substrates by direct-current reactive magnetron sputter epitaxy. Transmission electron microscopy (TEM) reveals clusters of dense stacking faults (SFs) regularly distributed along the c-axis. A strong emission line at ~3.42 eV

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associated with the basal-plane SFs has been observed in luminescence spectra. The optical signature of SFs is stable up to room temperatures with the activation energy of ~20 meV. Temperature-dependent time-resolved photoluminescence properties suggest that the recombination mechanism of the 3.42 eV emission can be understood in terms of multiple quantum wells self-organized along the growth axis of NRs. Tuning the electronic and magnetic properties of graphene-like AlN nanosheets by surface functionalization and thickness W. X. Zhang,a T. Li,a S. B. Gong,a C. He*b and L. Duana a School of Materials Science and Engineering, Chang'an University, Xi'an 710064, China b State Key Laboratory for Mechanical Behavior of Materials, School of Materials Science and Engineering, Xi'an Jiaotong University, Xi'an 710049, China Physical Chemistry Chemical Physics 2015,17, 10919-10924 http://dx.doi.org/10.1039/C5CP00123D

In this paper, the structural, electronic, and magnetic properties as well as the relative stabilities of fully and partially hydrogenated AlN nanosheets have been systematically investigated by first-principles calculations based on density functional theory. The results indicate that full hydrogenation is more energetically favorable for thinner AlN nanosheets, whereas semi-hydrogenation at N sites is preferred for thicker ones. Moreover, semiconductor → half-metal → metal transition with nonmagnetic → magnetic transfer can be achieved for AlN nanosheets by surface hydrogenation and increasing nanosheet thickness. The diverse electronic and magnetic properties highlight the potential applications of AlN nanosheets in electronics and spintronics. Terahertz detectors arrays based on orderly aligned InN nanowires Xuechen Chen, Huiqiang Liu, Qiuguo Li, Hao Chen, Rufang Peng, Sheng Chu & Binbin Cheng State Key Laboratory of Optoelectronic Materials and Technology, Sun Yat-Sen University, Guangdong Guangzhou 510275, China

School of Mobile Information Engineering, Sun Yat-Sen University, Guangdong Guangzhou 510275, China State Key Laboratory Cultivation Base for Nonmetal Composites and Functional Materials, Southwest University of Science and Technology, Sichuan Mianyang 621010, China Institute of Electrical Engineering, Chinese Academy of Engineering Physics, Mianyang 621423, China Scientific Reports Vol. 5, Article number: 13199 (2015) http://dx.doi.org/10.1038/srep13199

Nanostructured terahertz detectors employing a single semiconducting nanowire or graphene sheet have recently generated considerable interest as an alternative to existing THz technologies, for their merit on the ease of fabrication and above-room-temperature operation. However, the lack of alignment in nanostructure device hindered their potential toward practical applications. The present work reports ordered terahertz detectors arrays based on neatly aligned InN nanowires. The InN nanostructures (nanowires and nano-necklaces) were achieved by chemical vapor deposition growth, and then InN nanowires were successfully transferred and aligned into micrometer-sized groups by a “transfer-printing” method. Field effect transistors on aligned nanowires were fabricated and tested for terahertz detection purpose. The detector showed good photoresponse as well as low noise level. Besides, dense arrays of such detectors were also fabricated, which rendered a peak responsivity of 1.1 V/W from 7 detectors connected in series. High-temperature growth of GaN nanowires by molecular beam epitaxy: toward the material quality of bulk GaN Johannes K. Zettler, Christian Hauswald, Pierre Corfdir, Mattia Musolino, Lutz Geelhaar, Henning Riechert, Oliver Brandt, and Sergio Ferndández-Garrido Paul-Drude-Institut für Festkörperlektronik, Hausvogteiplatz 5 7, 10117 Berlin, Germany Crystal Growth & Design http://dx.doi.org/10.1021/acs.cgd.5b00690

In molecular beam epitaxy, the spontaneous formation of GaN nanowires on Si(111) substrates

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at elevated temperatures is limited by the long incubation time that precedes nanowire nucleation. In this work, we present three growth approaches to minimize the incubation time and to thus facilitate significantly higher growth temperatures (up to 875°C). We achieve this advancement by (i) using III/V flux ratios larger than one to compensate for Ga desorption, (ii) introducing a two-step growth procedure, and (iii) using an AlN buffer layer to favor GaN nucleation. The GaN nanowire ensembles grown at so far unexplored substrate temperatures exhibit excitonic transitions with sub-meV linewidths comparable to those of state-of-the-art free-standing GaN layers grown by hydride vapor phase epitaxy. Optical Emission of Individual GaN Nanocolumns Analyzed with High Spatial Resolution A. Urban †, M. Müller *‡, C. Karbaum ‡, G. Schmidt ‡, P. Veit ‡, J. Malindretos †, F. Bertram ‡, J. Christen ‡, and A. Rizzi † † IV. Physikalisches Institut, Georg-August-Universität Göttingen, 37077 Göttingen, Germany ‡ Institute of Experimental Physics, Otto-von-Guericke-University Magdeburg, 39106 Magdeburg, Germany Nano Letters http://dx.doi.org/10.1021/acs.nanolett.5b01278

Selective area growth has been applied to fabricate a homogeneous array of GaN nanocolumns (NC) with high crystal quality. The structural and optical properties of single NCs have been investigated at the nanometer-scale by transmission electron microscopy (TEM) and highly spatially resolved cathodoluminescence (CL) spectroscopy performed in a scanning transmission electron microscope (STEM) at liquid helium temperatures. TEM cross-section analysis reveals excellent structural properties of the GaN NCs. Sporadically, isolated basal plane stacking faults (BSF) can be found resulting in a remarkably low BSF density in the almost entire NC ensemble. Both, defect-free NCs and NCs with few BSFs have been investigated. The low defect density within the NCs allows the characterization of individual BSFs, which is of high interest for studying their optical properties. Direct nanometer-scale correlation of the CL and STEM data clearly exhibits a spatial correlation of the emission at

360.6 nm (3.438 eV) with the location of basal plane stacking faults of type I1.

NON/SEMI POLAR Information selected by

Philippe De Mierry (CRHEA-CNRS) Fabrication of InxGa1−xN/GaN QDs with InAlGaN capping layer by coaxial growth on non-(semi-) polar n-GaN NWs using metal organic chemical vapor deposition for blue emission Ji-Hyeon Park,a Arjun Mandal,a Dae-Young Um,a San Kang,a Da-som Leea and Cheul-Ro Lee*a a Semiconductor Materials Process Laboratory, School of Advanced Materials Engineering, Engineering College, Research Center for Advanced Materials Development (RCAMD), Chonbuk National University, Baekje-daero 567, Jeonju 561-756, Republic of Korea RSC Advances 2015,5, 47090-47097 http://dx.doi.org/10.1039/C5RA06836C

This article demonstrates for the first time the merits of an immediate InAlGaN capping layer over self-assembled InxGa1−xN/GaN quantum dots (QDs) coaxially grown on the m-plane and r-plane of n-GaN nanowires on Si (111) substrate using metal organic chemical vapor deposition. For comparative analysis, we prepared InGaN/GaN QD samples both with and without quaternary capping. InAlGaN capping layer acted as a strain-driven phase separation alloy. Inhomogeneous surface strain over the dots helped this quaternary alloy in forming an indium concentration gradient over InxGa1−xN QDs and thus, indium out-diffusion from the dots was reduced. Quaternary alloy capped samples exhibited vertically stacked, highly dense, pyramidal InxGa1−xN/GaN QDs of improved carrier confinement grown as the active region on n-GaN NWs. In contrast, the nonexistence of InAlGaN capping over InGaN/GaN QDs caused deformation of the dots due to In–Ga inter-diffusion between the dots and the GaN barrier layer. Three kinds of InxGa1−xN/GaN QDs of different x with an InAlGaN capping layer were fabricated coaxially on n-GaN nanowire, whose emission wavelength were 380 nm, 450 nm and 510 nm respectively. These coaxially fabricated InxGa1−xN/GaN QDs on defect free n-GaN

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nanowires have various excellent characteristics and can be widely applicable to new optoelectronics semiconductor devices. Intersubband transitions in nonpolar GaN/Al(Ga)N heterostructures in the short- and mid-wavelength infrared regions C. B. Lim1,2, M. Beeler1,2, A. Ajay1,2, J. Lähnemann1,2, E. Bellet-Amalric1,2, C. Bougerol1,3 and E. Monroy1,2 1 University Grenoble-Alpes, 38000 Grenoble, France 2 CEA, INAC-SP2M, 17 av. des Martyrs, 38000 Grenoble, France 3 CNRS, Institut Néel, 25 av. des Martyrs, 38000 Grenoble, France Journal of Applied Physics Vol. 118, 014309 (2015); http://dx.doi.org/10.1063/1.4926423

This paper assesses nonpolar m- and a-plane GaN/Al(Ga)N multi-quantum-wells grown on bulk GaN for intersubband optoelectronics in the short- and mid-wavelength infrared ranges. The characterization results are compared to those for reference samples grown on the polar c-plane, and are verified by self-consistent Schrödinger-Poisson calculations. The best results in terms of mosaicity, surface roughness, photoluminescence linewidth and intensity, as well as intersubband absorption are obtained from m-plane structures, which display room-temperature intersubband absorption in the range from 1.5 to 2.9 μm. Based on these results, a series of m-plane GaN/AlGaN multi-quantum-wells were designed to determine the accessible spectral range in the mid-infrared. These samples exhibit tunable room-temperature intersubband absorption from 4.0 to 5.8 μm, the long-wavelength limit being set by the absorption associated with the second order of the Reststrahlen band in the GaN substrates. Optical properties and structural investigations of (11-22)-oriented GaN/Al0.5Ga0.5N quantum wells grown by molecular beam epitaxy Daniel Rosales1,2, Bernard Gil1,2, Thierry Bretagnon1,2, Julien Brault3, Philippe Vennéguès3, Maud Nemoz3, Philippe de Mierry3, Benjamin Damilano3, Jean Massies3 and Pierre Bigenwald4 1 CNRS, Laboratoire Charles Coulomb, UMR 5221, F-34095 Montpellier, France 2 Université de Montpellier, Laboratoire Charles Coulomb, UMR 5221, F-34095 Montpellier, France

3 CNRS Centre de Recherche sur l'Hétéro-Epitaxie et ses Applications, 06560 Valbonne, France 4 Institut Pascal, Campus des Cézeaux, 24 avenue des Landais, 63171 Aubière Cedex, France Journal of Applied Physics Vol. 118, 024303 (2015) http://dx.doi.org/10.1063/1.4923306

We have grown (11-22)-oriented GaN/Al0.5Ga0.5N quantum wells (QWs) using molecular beam epitaxy on GaN (11-22)-oriented templates grown by metal-organic vapor phase epitaxy on m-plane oriented sapphire substrates. The performance of epitaxial growth of GaN/Al0.5Ga0.5N heterostructures on the semi-polar orientation (11-22) in terms of surface roughness and structural properties, i.e., strain relaxation mechanisms is discussed. In addition, high resolution transmission electron microscopy reveals very smooth QW interfaces. The photoluminescence of such samples are strictly originating from radiative recombination of free excitons for temperatures above 100 K. At high temperature, the population of localized excitons, moderately trapped (5 meV) at low temperature, is negligible. Ab initio-based study for surface reconstructions and adsorption behavior on semipolar AlN(11-22) surfaces during metal–organic vapor-phase epitaxy growth Yoshitaka Takemoto, Toru Akiyama, Kohji Nakamura and Tomonori Ito Department of Physics Engineering, Mie University, Tsu 514-8507, Japan Japanese Journal of Applied Physics Vol. 54; 085502 http://dx.doi.org/10.7567/JJAP.54.085502

The reconstructions and adsorption behavior of Al atoms on semipolar AlN($11\bar{2}2$) surfaces under various growth conditions are investigated by first-principles pseudopotential calculations. Our calculations reveal that there are several reconstructions depending on the growth conditions: the surface with Al adatoms is stabilized under H-poor conditions while that with Al–H and N–H bonds is favorable under H-rich

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conditions. We also find that the adsorption of Al atoms strongly depends on the surface reconstruction. The adsorption of Al atoms on the reconstructed surface under H-poor conditions is found to be much easier than that under H-rich conditions. These results indicate that similarly to the case of a polar AlN(0001) surface the growth of AlN on a semipolar ($11\bar{2}2$) surface during metal–organic vapor-phase epitaxy is prominent under H-poor conditions. Study of defect management in the growth of semipolar (11-22) GaN on patterned sapphire P Vennéguès, F Tendille and P De Mierry Centre de Recherche sur l'Hétéro-Epitaxie et ses Applications, Centre National de la Recherche Scientifique, CRHEA-CNRS, Rue Bernard Grégory, Sophia Antipolis, 06560 Valbonne, France Journal of Physics D: Applied Physics Vol. 48; 325103 http://dx.doi.org/10.1088/0022-3727/48/32/325103

This work describes, using mainly transmission electron microscopy as an investigation tool, the nature and behaviour of the crystalline defects which are present in (11-22) semipolar GaN films grown epitaxially on patterned r-sapphire substrates using a 3 step growth process. The microstructure at these different growth stages is described. The independent 3D-crystallites nucleated on the substrate surface contain threading dislocations resulting from the epitaxy on c-sapphire facets and basal stacking faults (BSFs), mainly in the  −c-wings. These defects are concentrated in a few hundred nanometre wide stripe-like regions emerging on the top facet of the islands. By a careful choice of the growth conditions, these defective regions may be overgrown by defect-free material, blocking their propagation towards the coalesced surface. However, when the 3D crystals coalesce, new dislocations together with very few BSFs are created at the coalescence boundaries. These coalescence defects propagate to the surface of the films in (0001) planes. In summary, the control of the nucleation and propagation of the crystalline defects allows obtaining large area semipolar films with very low defect densities: 7   ×   107 cm−2 for TDs and 70 cm−1 for BSFs.

Three-dimensional reciprocal space mapping with a two-dimensional detector as a low-latency tool for investigating the influence of growth parameters on defects in semipolar GaN Sondes Bauer,a* Sergey Lazarev,a Martin Bauer,b Tobias Meisch,c Marian Caliebe,c Va´clav Holy´,d Ferdinand Scholzc and Tilo Baumbacha a Synchrotron Facility ANKA, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, Eggenstein-Leopoldshafen, Germany b Precision Motors Deutsche Minebea GmbH, Villingen-Schwenningen, Germany, c Institute of Optoelectronics, Ulm University, Albert-Einstein-Allee 45, Ulm 89081, Germany, and dFaculty of Mathematics and Physics, Charles University in Prague, Ke Karlovu 5, Prague 2, 12116, Czech Republic Journal of Applied Crystallography Volume 48, Issue 4, pages 1000–1010, August 2015 http://dx.doi.org/10.1107/S1600576715009085

A rapid nondestructive defect assessment and quantification method based on X-ray diffraction and three-dimensional reciprocal-space mapping has been established. A fast read-out two-dimensional detector with a high dynamic range of 20 bits, in combination with a powerful data analysis software package, is set up to provide fast feedback to crystal growers with the goal of supporting the development of reduced defect density GaN growth techniques. This would contribute strongly to the improvement of the crystal quality of epitaxial structures and therefore of optoelectronic properties. The method of normalized three-dimensional reciprocal-space mapping is found to be a reliable tool which shows clearly the influence of the parameters of the metal–organic vapour phase epitaxial and hydride vapour phase epitaxial (HVPE) growth methods on the extent of the diffuse scattering streak. This method enables determination of the basal stacking faults and an exploration of the presence of other types of defect such as partial dislocations and prismatic stacking faults. Three-dimensional reciprocal-space mapping is specifically used in the manuscript to determine basal stacking faults quantitatively and to discuss the presence of partial dislocations. This newly developed method has been applied to semipolar GaN structures grown on patterned sapphire substrates (PSSs).

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The fitting of the diffuse scattering intensity profiles along the stacking fault streaks with simulations based on a Monte Carlo approach has delivered an accurate determination of the basal plane stacking fault density. Three-dimensional reciprocal-space mapping is shown to be a method sensitive to the influence of crystallographic surface orientation on basal stacking fault densities during investigation of semipolar (inline image) GaN grown on an r-plane (inline image) PSS and semipolar (inline image) GaN grown on an n-plane (inline image) PSS. Moreover, the influence of HVPE overgrowth at reduced temperature on the quality of semipolar (inline image) GaN has been studied. High-performance light-emitting diodes using hierarchical m-plane GaN nano-prism light extractors Siva Pratap Reddy M.,a Herie Park,a Se-Min Kim,a Seon-Ho Janga and Ja-Soon Jang*a a Department of Electronic Engineering, LED-IT Fusion Technology and Research Center (LIFTRC), Yeungnam University, Gyeongbuk 712-749, Republic of Korea Journal of Materials Chemistry C http://dx.doi.org/10.1039/C5TC01598G

We demonstrated high-performance GaN-based light-emitting diodes (LEDs) with hierarchical m-plane nano-prism light extractors on the n-GaN mesa sidewalls by using a tetramethylammonium hydroxide (TMAH)-based crystallographic etching technique. The crystallographic etching method leads to a chemically stable formation of hierarchical m-plane nano-prism structures as light extractors, increased p-carriers near the p-GaN surface, and the effective removal of the native oxides on the p-GaN surface. These results lead to considerable improvement of the p-ohmic contact properties between the p-GaN layer and the ITO electrode, remarkable device-performance characteristics, an improved efficiency droop, and a longer device lifetime. Based on the device-performance and the p-ohmic contact data, the hierarchical m-plane nano-prism structure acts as a multifunctional factor exhibiting high-efficiency photon-extraction, strong packaging effects, strong suppression of the leakage current along the

sidewalls from the p-GaN to the n-GaN, and/or a partial release of the piezoelectric field across the quantum well region. Doping behavior of (112‾2) GaN grown on patterned sapphire substrates Tobias Meisch1,*, Raphael Zeller1, Sabine Schörner2, Klaus Thonke2, Lutz Kirste3, Theo Fuchs3 and Ferdinand Scholz1 1Institute of Optoelectronics, University of Ulm, Albert-Einstein-Allee 45, 89081 Ulm, Germany 2Institute of Quantum Matter, University of Ulm, Albert-Einstein-Allee 45, 89081 Ulm, Germany 3Fraunhofer Institute for Applied Solid State Physics, Tullastrasse 72, 79108 Freiburg, Germany Physica status solidi (b) http://dx.doi.org/10.1002/pssb.201552241

We present results of the investigation on the doping behavior of planar semipolar inline image-oriented GaN grown on inline image patterned sapphire substrates mainly focusing on the magnesium incorporation. We observed that Mg is incorporated with much lower efficiency into the inline image plane as compared to polar c-plane GaN. This problem could be decreased by varying the growth temperature. We found higher Mg concentrations with constant Mg flow for reduced growth temperature. Simultaneously, the parasitic background carrier concentration was reduced. Using this optimization, a planar semipolar InGaN/GaN-LED on inline image-oriented GaN was grown. Electroluminescence measurements show reasonable electrical and optical performance Growth of semipolar {20–21} GaN and {20–2–1} GaN for GaN substrate Yasuhiro Hashimoto1,*, Keisuke Yamane2, Narihito Okada1 and Kazuyuki Tadatomo1 1Graduate School of Science and Engineering, Yamaguchi University, 2-16-1 Tokiwadai, Ube, Yamaguchi 755-8611, Japan 2Department of Electrical and Electronic Information Engineering, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580, Japan Physica status solidi (b) http://dx.doi.org/10.1002/pssb.201552271

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In this article, we present a semipolar {20–21} GaN layer and {20–2–1} GaN layer for large GaN substrates. The {20–21} GaN layer was fabricated on {22–43} patterned sapphire substrates (PSSs) by metal-organic vapor-phase epitaxy (MOVPE) and hydride vapor-phase epitaxy (HVPE). We found that the surface roughening and crack generation during the HVPE growth were suppressed by the formation of SiO2-striped masks parallel to the c-axis on the MOVPE-grown {20–21} GaN template. Furthermore, we demonstrated millimeter-thick crystal growth on a {20–21} GaN layer and a {20–2–1} GaN layer on a GaN substrate using HVPE. The dark-spot density in the {20–2–1} GaN layer was approximately 9.6 × 106 cm−2 for 960 min growth. The dark-spot density in the {20–2–1} GaN layer decreased more rapidly than that in the {20–21} GaN layer as growth thickness increased. Radiative and nonradiative recombination mechanisms in nonpolar and semipolar GaInN/GaN quantum wells Torsten Langer1,2,*, Manuela Klisch1, Fedor Alexej Ketzer1, Holger Jönen1, Heiko Bremers1,2, Uwe Rossow1, Tobias Meisch3, Ferdinand Scholz3 and Andreas Hangleiter1,2 1Institut für Angewandte Physik, Technische Universität Braunschweig, Mendelssohnstraße 2, 38106 Braunschweig, Germany 2Laboratory for Emerging Nanometrology, Technische Universität Braunschweig, Mendelssohnstraβe 2, 38106 Braunschweig, Germany 3Institut für Optoelektronik, Universität Ulm, Albert-Einstein-Allee 45, 89081 Ulm, Germany Physica status solidi (b) http://dx.doi.org/10.1002/pssb.201552353

Via temperature-dependent time-resolved photoluminescence spectroscopy, we investigate the radiative and nonradiative recombination processes in thin (quantum well widths of about 1.5 nm) a-plane, m-plane, (inline image) and (inline image) GaInN/GaN fivefold quantum well structures of varying indium content grown on low defect density GaN substrates and GaN templates. At room temperature, we observe surprisingly short radiative lifetimes in the range from 100 ps to 1 ns for these structures, being about one to two orders of magnitude shorter

than for similar c-plane quantum wells. This large difference cannot solely be explained by the larger overlap matrix element in non- and semipolar wells. Higher exciton binding energies and lower effective density of states masses may contribute to an enhanced radiative probability. The nonradiative recombination exhibits a thermally activated behavior with activation energies of about 10 meV for (inline image) and around 25 meV for nonpolar quantum wells. These values are lower than the quantum well barrier height and the exciton binding energy, but in a similar range as the localization energies estimated from the radiative recombination. Growth and coalescence studies of (112‾2) oriented GaN on pre-structured sapphire substrates using marker layers Marian Caliebe1,*, Yisong Han2, Matthias Hocker3, Tobias Meisch1, Colin Humphreys2, Klaus Thonke3 and Ferdinand Scholz1 1Institute of Optoelectronics, Ulm University, Albert-Einstein-Allee 45, 89081 Ulm, Germany 2Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS, United Kingdom 3Institute of Quantum Matter, Semiconductor Physics Group, Ulm University, Albert-Einstein-Allee 45, 89081 Ulm, Germany Physica status solidi (b) http://dx.doi.org/10.1002/pssb.201552266

In this article, the growth and coalescence of semi-polar inline image oriented GaN layers, deposited on pre-structured r-plane sapphire substrates, is studied with the help of Si-doped marker layers. It has been found to be very important to adjust the shape of the initial GaN stripes by varying the growth temperature to obtain not only a smooth surface, but also a small density of basal plane stacking faults (BSFs) and threading dislocations (TDs) on the wafer surface. With the help of transmission electron microscopy (TEM) and cathodoluminescence measurements (CL), we can conclude that during growth, we need to achieve a compromise between small BSF density, small TD density, and perfect coalescence with smooth surface, free of fissures, and other growth artifacts. Also the formation of arrow-head-shaped surface artifacts called “chevrons”

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[1, 2] can be understood to be caused by imperfect coalescence. We observe with the help of the marker layers that the growth rate fluctuates between neighboring stripes. This effect strongly increases for higher growth temperature Polarization characteristics of 480-680 nm (11View the MathML source2¯2) InGaN/GaN quantum well structures with strain relaxation effects Seoung-Hwan Park Department of Electronics Engineering, Catholic University of Daegu, Hayang, Kyeongbuk 712-702, South Korea Superlattices and Microstructures http://dx.doi.org/10.1016/j.spmi.2015.08.009

The polarization characteristics as a function of the In composition for semipolar (11View the MathML source2¯2) InGaN/GaN quantum well (QW) structures with strain relaxation effects are investigated by using the multiband effective-mass theory. We assumed that the strain relaxation ratio View the MathML source(∊y′y′0-∊y′y′)/∊y′y′0 is linearly proportional to the difference in the lattice constants between the well and the substrate. The energy spacing between the first two subbands increases with increasing In composition, and the average hole effective mass of the first subband is reduced for a QW structure with a larger In composition. The [View the MathML source1¯1¯23] x′x′-polarized matrix elements are shown to be much larger than the [1View the MathML source1¯00] y′y′-polarized matrix elements. As a result, the x′x′-polarized light emission is shown to be dominant and a weak function of the In composition. On the other hand, the light emission for y′y′-polarizations rapidly decreases with increasing In composition, mainly due to a decrease in the matrix elements. Thus, the absolute value of the polarization ratio rapidly increases with increasing transition wavelength.

Probing the correlation between structure, carrier dynamics and defect states of epitaxial GaN film on (1120) sapphire grown by rf-molecular beam epitaxy Shibin Krishna T C a†, Neha Aggarwal a†, G. Anurag Reddy a†, Palak Dugar a, Monu Mishra a†, Lalit Goswami a, Nita Dilawar b, Mahesh Kumar a, K K Maurya c and Govind Gupta a † 5 * aPhysics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr K S Krishnan Road, New Delhi-110012, India bApex Level Standards & Industrial Metrology, CSIR-National Physical Laboratory, Dr K S Krishnan Road, New Delhi-110012, India cSophisticated and Analytical Instrumentation, CSIR-National Physical Laboratory, Dr. K.S. Krishnan Road, New Delhi-110012, India †10 Academy of Science & Innovative Research (AcSIR), CSIR-NPL Campus, Dr. K.S. Krishnan Road, New Delhi-110012, India RSC Advances http://dx.doi.org/10.1039/C5RA10099B

A systematic study has been performed to correlate structural, optical and electrical properties with defect states in the GaN films grown on a-plane (112 @#x0305;0) Sapphire substrate via rf-plasma molecular beam epitaxy. Morphological analysis reveals the presence of small lateral size (30-70 nm) hexagonally shaped V- pits on the GaN films. These V-defects possibly contribute as the main source of non-radiative decay. High resolution X-ray diffraction reveals highly single crystalline GaN film grown on a-plane sapphire substrate where the threading dislocations are the cause of V-defects in the GaN film. Photoluminescence measurement shows a highly luminescence band to band emission of GaN film at 3.41 eV along with a broad defect band emission centered at 2.2 eV. A detailed optical and electrical analysis has been carried out to study the defects states and related carrier dynamics for determining the efficacy of the film for device fabrication. The variation in the low temperature current voltage measurements confirms the presence of deep level defects in mid- band gap region while transient spectroscopy shows that non radiative decay is the dominant relaxation mechanism for the photo excited-carriers from these defect states.

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Structural properties of bulk GaN substrates: Impact of structural anisotropy on non-polar and semi-polar crystals Jarosław Serafińczuk1,*, Robert Kucharski2, Marcin Zając2, Teodor Paweł Gotszalk1 and Robert Kudrawiec3 "1 Faculty of Microsystem Electronics and Photonics, Wroclaw University of Technology, Wroclaw, Poland 2Ammono SA, Warsaw, Poland 3Faculty of Fundamental Problems of Technology, Wroclaw University of Technology, Wroclaw, Poland Crystal Research and Technology http://dx.doi.org/10.1002/crat.201500125

In this paper we show the structural parameters and structural anisotropy of the bulk GaN substrates of various crystallographic orientations (00.1), (10.0), (11.0) and (20.1) obtained by ammonothermal method. The structural parameters were investigated using high resolution X-Ray Diffraction. Perfect crystalline structure manifests in very narrow peaks in X-ray rocking curves. The full width at half maximum (FWHM) values of 16 and 18 arcsec for the symmetrical and asymmetrical peaks, respectively, have been observed. In addition, we observed structural anisotropy in the non-polar and semi-polar crystals, depending on the orientation of the sample relative to the X-ray beam. It is conducted that this anisotropy is a intrinsic property of non-polar and semi-polar GaN substrates. Bottom-Up Nano-heteroepitaxy of Wafer-Scale Semipolar GaN on (001) Si Jui-Wei Hus1, Chien-Chia Chen1, Ming-Jui Lee1, Hsueh-Hsing Liu2, Jen-Inn Chyi2, Michael R. S. Huang3, Chuan-Pu Liu3, Tzu-Chiao Wei4, Jr-Hau He5 and Kun-Yu Lai1,* 1Department of Optics and Photonics, National Central University, Chung-Li, Taiwan 2Department of Electrical Engineering, National Central University, Chung-Li, Taiwan 3Department of Materials Science and Engineering, National Cheng Kung University, Tainan, Taiwan 4Institute of Photonics and Optoelectronics, National Taiwan University, Taipei, Taiwan 5Computer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division, King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia

Advanced Materials http://dx.doi.org/10.1002/adma.201501538

Semipolar inline image InGaN quantum wells are grown on (001) Si substrates with an Al-free buffer and wafer-scale uniformity. The novel structure is achieved by a bottom-up nano-heteroepitaxy employing self-organized ZnO nanorods as the strain-relieving layer. This ZnO nanostructure unlocks the problems encountered by the conventional AlN-based buffer, which grows slowly and contaminates the growth chamber. A study of the piezoelectric properties of semipolar inline image GaN/AlN quantum dots D. Young, G. Jurczak, A. Lotsari, G. P. Dimitrakopulos, Ph. Komninou and P. Dłużewski 1Division of Computational Methods, Institute of Fundamental Technological Research of the Polish Academy of Sciences, ul. Pawińskiego 5b, 02-106 Warsaw, Poland 2Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece Physica status solidi (b) http://dx.doi.org/10.1002/pssb.201552156

GaN quantum dots grown in (inline image)’orientated AlN are studied. The inline image-nucleated quantum dots exhibit rectangular- or trapezoid-based truncated pyramidal morphology. Another quantum dot type orientated on inline image is reported. Based on high-resolution transmission microscopy and crystal symmetry, the geometry of inline image-orientated quantum dots is proposed. A piezoelectric model is used within a finite element method to determine and compare the strain-state and electrostatic potential associated with the quantum dot morphology and an estimation of the band-edge energy is made. We report on some novel properties of the inline image-orientated quantum dot, including mixed strain-states and strain-state bowing.

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OTHER Information selected by

Agnès Trassoudaine (Université d'Auvergne) and Yvon Cordier (CRHEA-CNRS)

Effect of target–substrate distance on the quality of AlN films grown on Si(110) substrates by pulsed laser deposition Weijia Yanga, Wenliang Wanga, Yunhao Lina, Shizhong Zhoua, Ying Liuc, Guoqiang Lia, b, a State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China b Department of Electronic Materials, School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China c College of Field Engineering, PLA University of Science & Technology, Nanjing 210007, China Materials Letters Volume 160, 1 December 2015, Pages 20–23 http://dx.doi.org/10.1016/j.matlet.2015.07.069

Effect of target–substrate distance on the quality of AlN films grown on Si(110) substrates by pulsed laser deposition (PLD) is carefully studied. It is found that the quality of AlN films is firstly improved and then is deteriorated as the target–substrate distance increases from 5 to 10 cm, and we find that 8 cm is the appropriate target–substrate distance for achieving high-quality AlN films on Si(110) substrates by PLD. The as-grown ~400 nm-thick AlN films show flat surface with a root-mean-square surface roughness of 1.8 nm. Meanwhile, there is no interfacial layer existing in the AlN/Si(110) interface. This work is paramount importance for the fabrication of AlN-based devices on Si(110) substrates by PLD. Self-generated microcracks in an ultra-thin AlN/GaN superlattice interlayer and their influences on the GaN epilayer grown on Si(110) substrates by metal–organic chemical vapor deposition Xu-Qiang Shen,*a Tokio Takahashi,a Hirofumi Matsuhata,a Toshihide Idea and Mitsuaki Shimizua a Advanced Power Electronics Research Center, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Central 2, CrystEngComm 2015,17, 5014-5018

http://dx.doi.org/10.1039/C5CE00929D

We investigated the effect of an ultra-thin AlN/GaN superlattice interlayer (SL IL) on the GaN epilayer grown on Si(110) substrates by metal–organic chemical vapor deposition (MOCVD). It is found that microcracks (MCs) are self-generated in the SL IL region, which depend on the thickness of the SL IL. The MCs influence the characteristics of the GaN epilayers grown on the SL IL, such as surface morphologies, strain and structural qualities. Furthermore, different MC configurations depending on the SL IL thickness are observed, which imply the controllability of MC generation. Understanding of the mechanism and the optimization of the SL IL structure make it possible to grow crack-free high-quality GaN films on Si substrates for optical and electronic device applications. Graphene-like AlN layer formation on (111) Si surface by ammonia molecular beam epitaxy V. Mansurova, T. Malina, Yu. Galitsyna, K. Zhuravleva, b a Rzhanov Institute of Semiconductor Physics of Siberian Branch of Russian Academy of Sciences, Lavrentiev 13, 630090 Novosibirsk, Russia b Novosibirsk State University, 630090 Novosibirsk, Russia Journal of Crystal Growth Volume 428, 15 October 2015, Pages 93–97 http://dx.doi.org/10.1016/j.jcrysgro.2015.07.030

The formation of a graphene-like AlN (g-AlN) layer on a (111)-oriented silicon substrate in ammonia molecular beam epitaxy (MBE) has been investigated by the RHEED method. A flat AlN layer with a thickness of a few monolayers was formed by the deposition of Al atoms onto a highly ordered SiN-(8×8) surface prepared on the atomically flat (111)Si substrate under an ammonia flux. An unusual (4×4) structure of g-AlN on the Si surface was found. The exact coincidence of the fundamental (0 1) AlN streak and the fractional-order (0 5/4) beam of the (4×4) RHEED structure allows us to measure precisely the in-plane lattice parameters of g-AlN. The g-AlN lattice constant of 3.08 Å is found in a good agreement with the ab initio calculations performed recently. The evolution of the g-AlN in-plane lattice constant during the initial stages of

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the g-AlN formation and transformation to the bulk wurtzite AlN was analyzed. Band alignment at AlN/Si (111) and (001) interfaces Sean W. King1,a), Robert J. Nemanich2,b) and Robert F. Davis1,c) 1 Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA 2 Department of Physics, North Carolina State University, Raleigh, North Carolina 27695, USA Journal of Applied Physics Vol. 118, 045304 (2015) http://dx.doi.org/10.1063/1.4927515

To advance the development of III-V nitride on silicon heterostructure semiconductor devices, we have utilized in-situ x-ray photoelectron spectroscopy (XPS) to investigate the chemistry and valence band offset (VBO) at interfaces formed by gas source molecular beam epitaxy of AlN on Si (001) and (111) substrates. For the range of growth temperatures (600–1050 °C) and Al pre-exposures (1–15 min) explored, XPS showed the formation of Si-N bonding at the AlN/Si interface in all cases. The AlN/Si VBO was determined to be −3.5 ± 0.3 eV and independent of the Si orientation and degree of interfacial Si-N bond formation. The corresponding AlN/Si conduction band offset (CBO) was calculated to be 1.6 ± 0.3 eV based on the measured VBO and band gap for wurtzite AlN. Utilizing these results, prior reports for the GaN/AlN band alignment, and transitive and commutative rules for VBOs, the VBO and CBO at the GaN/Si interface were determined to be −2.7 ± 0.3 and −0.4 ± 0.3 eV, respectively. Growth and characterization of high quality AlN using combined structure of low temperature buffer and superlattices for applications in the deep ultraviolet Jinwan Kim, Jaedo Pyeon, Minhwan Jeon and Okhyun Nam Convergence Center for Advanced Nano Semiconductor (CANS), Korea Polytechnic University, Siheung, Gyeonggi 429-793, Republic of Korea Japanese Journal of Applied Physics Vol. 54; 081001

http://dx.doi.org/10.7567/JJAP.54.081001

This study reports on the growth and characterization of AlN/AlxGa1−xN superlattices (SLs) for reduction of threading dislocations to grow high quality AlN layer. Insertion of optimized SLs is shown to effectively reduce the dislocation density, there by resulting in a high crystal quality 2.5-µm-thick AlN layer. It was found that full width at half-maximum (FWHM) of X-ray rocking curves (XRCs) around both (0002) and $(10\bar{1}2)$ diffraction were decreased to 230 and 420, respectively. The results of XRC FWHM and dislocation densities from etch pit density (EPD) by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) micrographs are in a good agreement. This high quality and low dislocation density AlN layer is of key importance for high efficiency deep-UV light emitting diodes and power devices. Low-resistivity m-plane freestanding GaN substrate with very low point-defect concentrations grown by hydride vapor phase epitaxy on a GaN seed crystal synthesized by the ammonothermal method Kazunobu Kojima1, Yusuke Tsukada2, Erika Furukawa1, Makoto Saito1,2, Yutaka Mikawa2, Shuichi Kubo2, Hirotaka Ikeda2, Kenji Fujito2, Akira Uedono3 and Shigefusa F. Chichibu1 1 Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577, Japan 2 Gallium Nitride Department, Mitsubishi Chemical Corporation, Ushiku, Ibaraki 300-1295, Japan 3 Division of Applied Physics, Faculty of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan Applied Physics Express Vol. 8 095501 http://dx.doi.org/10.7567/APEX.8.095501

An m-plane freestanding GaN substrate satisfying both low resistivity (? = 8.5 × 10?3 ?centerdotcm) and a low point-defect concentration, being applicable to vertically conducting power-switching devices, was grown by hydride vapor phase epitaxy on a nearly bowing-free bulk GaN seed wafer synthesized by the ammonothermal method in supercritical ammonia using an acidic mineralizer. Its threading dislocation and basal-

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plane staking-fault densities were approximately 104 cm?2 and lower than 100 cm?1, respectively. A record-long fast-component photoluminescence lifetime of 2.07 ns at room temperature was obtained for the near-band-edge emission, reflecting a significantly low concentration of nonradiative recombination centers composed of Ga vacancies. High-quality, large-area MoSe2 and MoSe2/Bi2Se3 heterostructures on AlN(0001)/Si(111) substrates by molecular beam epitaxy E. Xenogiannopoulou,a P. Tsipas,a K. E. Aretouli,a D. Tsoutsou,a S. A. Giamini,a C. Bazioti,b G. P. Dimitrakopulos,b Ph. Komninou,b S. Brems,c C. Huyghebaert,c I. P. Raduc and A. Dimoulas*a a Institute of Nanoscience and Nanotechnology, NCSR DEMOKRITOS, Athens, Greece b Physics Department, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece c Imec, Kapeldreef 75, Leuven, Belgium " Nanoscale 2015,7, 7896-7905 http://dx.doi.org/10.1039/C4NR06874B

Atomically-thin, inherently 2D semiconductors offer thickness scaling of nanoelectronic devices and excellent response to light for low-power versatile applications. Using small exfoliated flakes, advanced devices and integrated circuits have already been realized, showing great potential to impact nanoelectronics. Here, high-quality single-crystal MoSe2 is grown by molecular beam epitaxy on AlN(0001)/Si(111), showing the potential for scaling up growth to low-cost, large-area substrates for mass production. The MoSe2 layers are epitaxially aligned with the aluminum nitride (AlN) lattice, showing a uniform, smooth surface and interfaces with no reaction or intermixing, and with sufficiently high band offsets. High-quality single-layer MoSe2 is obtained, with a direct gap evidenced by angle-resolved photoemission spectroscopy and further confirmed by Raman and intense room temperature photoluminescence. The successful growth of high-quality MoSe2/Bi2Se3 multilayers on AlN shows promise for novel devices exploiting the non-trivial topological properties of Bi2Se3.

Sulfur doping of AlN and AlGaN for improved n-type conductivity Luke Gordon1, Joel B. Varley1,2, John L. Lyons1,3, Anderson Janotti1 and Chris G. Van de Walle1,* 1Materials Department, University of California, Santa Barbara, USA 2Lawrence Livermore National Laboratory, Livermore, USA 3Present address: Center for Functional Nanomaterials, Brookhaven National Laboratories, Upton, USA Physica status solidi (RRL) - Rapid Research Letters http://dx.doi.org/10.1002/pssr.201510165

Achieving high levels of n-type conductivity in AlN and high Al-content nitride alloys is a long standing problem; significant decreases in conductivity are observed as the Al content is increased, a phenomenon that has been attributed to donors such as oxygen or silicon forming DX centers. We address this problem through a comprehensive first-principles hybrid density functional study of potential n-type dopants, identifying SN and SeN as two elements which are potential shallow donors because they do not undergo a DX transition. In particular, SN is highly promising as an n-type dopant because it also has a low formation energy and hence a high solubility. Significant reduction of AlN wafer bowing grown on sapphire substrate with patterned graphene oxide Joo Jina, Tran Viet Cuonga, b, Min Hana, Beo Deul Ryua, Ko Ku Kanga, Chang-Hee Honga a LED Agri-bio Fusion Technology Research Center, School of Semiconductor and Chemical Engineering, Chonbuk National University, Jeonju 561-756, Korea b Department of Solid State Physics, Faculty of Physics, University of Science, Vietnam National University in Ho Chi Minh City (VNU-HCM), 227 Nguyen Van Cu, District 5, Ho Chi Minh City, Vietnam Materials Letters http://dx.doi.org/10.1016/j.matlet.2015.07.162

We demonstrated experimentally that an approximate 15% reduction in wafer bowing was achieved by spray-coating of graphene oxide (GO) with an O-ring pattern on the sapphire substrate before the metal organic chemical vapor deposition-grown AlN template. At the 1350 °C

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growth temperature of AlN, GO was thermally reduced to graphene, which is favorable to alleviate thermal compressive stress between the AlN template and sapphire substrate during the cooling process due to the natural high thermal conductivity of graphene. Consequently, the GO O-ring pattern can play an important role in dramatically reduce cracks, edge delamination and threading dislocation density of AlN templates grown on sapphire substrates. Integration of epitaxial Pb(Zr0.52Ti0.48)O3 films on GaN/AlGaN/GaN/Si(111) substrates using rutile TiO2 buffer layers K. Elibola, M.D. Nguyena, b, c, R.J.E. Huetinga, D.J. Gravesteijna, d, G. Kostera, G. Rijndersa a MESA + Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500AE Enschede, The Netherlands b SolMateS B.V., Drienerlolaan 5, Building 6, 7522NB Enschede, The Netherlands c International Training Institute for Materials Science, Hanoi University of Science and Technology, No.1 Dai Co Viet road, Hanoi 10000, Vietnam d NXP Semiconductors Research, High Tech Campus 46, 5656AE Eindhoven, The Netherlands Thin Solid Films http://dx.doi.org/10.1016/j.tsf.2015.07.069

The integration of ferroelectric layers on gallium nitride (GaN) offers a great potential for various applications. Lead zirconate titanate (PZT), in particular Pb(Zr0.52Ti0.48)O3, is an interesting candidate. For that a suitable buffer layer should be grown on GaN in order to prevent the reaction between PZT and GaN, and to obtain PZT with a preferred orientation. Here, we study pulsed laser deposited (100) rutile titanium oxide (R-TiO2) as a potential buffer layer candidate for ferroelectric PZT. For this purpose, the growth, morphology and the surface chemical composition of R-TiO2 films were analysed by reflection high-energy electron diffraction, atomic force microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. We find optimally (100) oriented R-TiO2 growth on GaN (0002) using a 675 °C growth temperature and 2 Pa O2 deposition pressure as process conditions. More importantly, the R-TiO2 buffer layer grown on GaN/Si substrates prevents the unwanted formation of the PZT pyrochlore

phase. Finally, the remnant polarization and coercive voltage of the PZT film on TiO2/GaN/Si with an interdigitated-electrode structure were found to be 25.6 μC/cm2 and 8.1 V, respectively. Formation of definite GaN p–n junction by Mg-ion implantation to n−-GaN epitaxial layers grown on a high-quality free-standing GaN substrate Takuya Oikawa, Yusuke Saijo, Shigeki Kato, Tomoyoshi Mishima, Tohru Nakamura Department of Electronics and Electrical Engineering, Hosei University, Tokyo, Japan Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms http://dx.doi.org/10.1016/j.nimb.2015.07.095

P-type conversion of n−-GaN by Mg-ion implantation was successfully performed using high quality GaN epitaxial layers grown on free-standing low-dislocation-density GaN substrates. These samples showed low-temperature PL spectra quite similar to those observed from Mg-doped MOVPE-grown p-type GaN, consisting of Mg related donor–acceptor pair (DAP) and acceptor bound exciton (ABE) emission. P–n diodes fabricated by the Mg-ion implantation showed clear rectifying I–V characteristics and UV and blue light emissions were observed at forward biased conditions for the first time. Energy Impacts of Wide Band Gap Semiconductors in U.S. Light-Duty Electric Vehicle Fleet Joshua A Warren , Matthew E Riddle , Diane J. Graziano , Sujit Das , Venkata K.K. Upadhyayula , Eric Masanet , and Joe Cresko † Oak Ridge National Laboratory, Oak Ridge, TN, ‡ Argonne National Laboratory, Argonne, IL, § Northwestern University, Evanston, IL, ^U.S. Department of Energy, Washington, DC Environmental Science & Technology http://dx.doi.org/10.1021/acs.est.5b01627

Silicon carbide and gallium nitride, two leading wide band gap semiconductors with significant potential in electric vehicle power electronics, are examined from a life cycle energy perspective and compared with incumbent silicon in U.S. light-duty electric vehicle fleet. Cradle-to-gate, silicon

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carbide is estimated to require more than twice the energy as silicon. However, the magnitude of vehicle use phase fuel savings potential is comparatively several orders of magnitude higher than the marginal increase in cradle-to-gate energy. Gallium nitride cradle-to-gate energy requirements are estimated to be similar to silicon, with use phase savings potential similar to or exceeding that of silicon carbide. Potential energy and carbon emissions reductions in the United States vehicle fleet are examined through several scenarios that consider the market adoption potential of electric vehicles themselves, as well as the market adoption potential of wide band gap semiconductors in electric vehicles. For the 2015 – 2050 timeframe, cumulative energy savings associated with the deployment of wide band gap semiconductors are estimated to range from 2 – 20 billion GJ depending on market adoption dynamics.

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PRESS RELEASE Technical and economic information selected by Knowmade

OPTOELECTRONICS

LED lighting to reach 32% of office lamp revenue in 2015 Semiconductor Today

LED lighting is forecast to reach 32% of total lamp revenue in office lighting in 2015, according to the latest projection by market research firm IHS Inc. Global revenue for office lamps is projected to be $3.5bn, of which $1.2bn is expected to be LED. The remainder is mostly fluorescent lighting. LED lighting is gaining popularity in high-end installations in developed countries. Also, lighting designers are increasingly eschewing fluorescent lighting in their projects, in favor of LEDs. The key factors used to make decisions about office lighting installations are the following: upfront cost, running cost (i.e. electricity cost) and the ease and frequency of maintenance. LED lighting does well in most of these categories. However, one notable exception is the initial installation cost, which is higher than other technologies. In office lighting projects installed in 2014, maintenance accounted for 18% of project cost, compared with 51% for equipment, 25% for installation, and 6% for design and engineering. Increasing use of LED lighting is only part of the story, as the lighting industry is also a shifting toward smart lighting. Smart-lighting solutions are only used in a small number of offices globally, but there are many different types of systems available. According to one US-based lighting designer, "occupancy and vacancy sensing is essential and, depending on where you are in the country, also daylight sensing". Smart lighting is most commonly introduced to meet legislative requirements to save energy. Where such regulations do not exist, its penetration rate is currently still very low, notes IHS. Technology challenges also exist in office lighting, but none are insurmountable, says the market research firm. One of the biggest issues today is

dimming, with a wide variety of control standards available. Until organizations have a more coherent collaboration, the market will remain inhibited, IHS reckons. It would be beneficial to the industry to improve this in the next few years, it concludes. Read more Large lighting makers continue to transition to LEDs Semiconductor Today

As a proportion of total global lamp revenue, LED lamp revenue grew from 25% in 2013 to 30% in 2014 and is forecast to reach 67% in 2022 as the lighting market continues to transition to LED technology, according to a research note from Fabian Hoelzenbein, market analyst for Lighting & LEDs at market research firm IHS Technology. A growing market for LED technology lighting means a shrinking market for halogen, compact fluorescent lamp (CFL) and other traditional technologies, and the larger lighting companies have struggled to adapt their businesses accordingly. At the same time, smaller and more specialized LED-only companies have entered the market, further increasing the pressure on the incumbent players, notes IHS. Market leader Philips managed to increase its share in the LED lamp market, from 14% in 2013 to 17% in 2014. Runners-up Osram, Panasonic and Toshiba roughly maintained their market shares of 8%, 6% and 6%, respectively, while GE increased from 3% in 2013 to 6% in 2014. Hefty losses in the traditional technology lamp market, however, meant that all top-five lamp manufacturers lost market share overall. The luminaire market is a lot more fragmented than the lamp market. Philips is the worldwide market leader, with 6% of the market, and the top 10 manufacturers combined comprise just 22% of the market. Overall though, the luminaire market looks a bit brighter than the lamp market, at least for the top players. The top five companies — Philips, Acuity, Panasonic, Zumtobel and Cooper

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— all held on to their respective market shares in 2014. However, the pull of LED technology is also felt in the luminaire market. LED luminaire revenue market share grew from 21% in 2013 to 23% in 2014, and is expected to reach 53% in 2022. IHS says that the big winner is Philips, whose LED luminaire market share increased from 4% in 2013 to 10% in 2014. Acuity Brands, which is focused on the American market, saw its share increase from 4% in 2013 to 6% in 2014. Acuity Brands holds 19% of the overall LED luminaire market (up from 16% in 2013). Philips is more concentrated, with 12% of the European, Middle East & Africa (EMEA) market and 10% of the Asia-Pacific (APAC) market. It remains to be seen how leading lighting manufacturers will follow the market as it moves towards LEDs, says IHS. However, a strong focus on the luminaire market seems to help ease this transition … at least for the moment, the firm concludes. Read more LED grow-light market rising at nearly 27% CAGR to $1.9bn by 2020 Semiconductor Today

The light-emitting diode (LED) grow-light market will rise at a compound annual growth rate (CAGR) of 26.93% from 2015 to more than $1.9bn by 2020, according to the report 'LED Grow Light Market by Wattage, Type of Installation (New, Retrofit), Spectrum (Partial, Full), Application (Indoor Farming, Commercial Greenhouse, Vertical Farming, Turf & Landscaping, Research, and Others), and Geography - Forecast to 2020' from MarketsandMarkets. The LED grow-light market is expected to witness a high-growth phase in applications such as vertical farming, commercial greenhouse, and indoor farming. LED grow-lights were used initially for indoor farming, but with increasing awareness about their benefits (such as energy efficiency, no need for a ballast, and low heat emission) large-scale adoption has begun in vertical farming and commercial greenhouse applications. Also, the rising trend for indoor farming, government regulations favoring LED lighting, and the requirement for energy-efficient and long-lasting lighting technology as a supplement to natural

lighting in plant growth, are all driving growth in the LED grow-light market. Europe is estimated to account for the major share of the market, whereas the Asia-Pacific (APAC) region is expected to see the fastest growth and overtake North America. The new opportunities will not only drive the LED grow-light market in the coming years but will also lead to the opening up new market segments, forecasts the report. The major players in the market are listed as Alta LED Corp (USA), Bridgelux Inc (USA), Cree Inc (USA), Everlight Electronics Co Ltd (Taiwan), General Electric Company (USA), Heliospectra AB (Sweden), Illumitex Inc (USA), Lumigrow Inc (USA), Osram Licht AG (Germany), and Royal Philips Electronics N.V. (The Netherlands). Read more LEDs reach 19% penetration of transportation lamp market revenue Semiconductor Today

Light-emitting diode (LED) lamps in transportation lighting will rise to $0.2bn in 2015, reaching 19% of the total $1bn transportation lamp market, forecasts market research firm IHS Inc according to a Research Note from Jamie Fox, principal analyst for Lighting and LEDs. LEDs, which are increasing their market penetration, generally have high initial installation cost but lower maintenance and energy costs. The other main technology is high-intensity discharge (HID). The key factors used to make decisions about transportation lighting installations are security, quality of light, upfront costs, running costs, and ease of maintenance. LEDs do well in most of these categories, says IHS, but one notable exception is initial installation cost, which is higher than other technologies. In transportation lighting projects installed in 2014, service and maintenance accounted for 21% of project cost, compared with 58% for equipment, 17% for installation, and 4% for design and engineering. Increasing use of LED lighting is only part of the story, as the lighting industry is also a shifting toward smart lighting, which is just beginning to penetrate the transportation sector (especially in urban street lighting), notes the market reseach firm. The reasons for the shift to smart lighting are

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two-fold. First, it is common to dim or turn off lighting, depending on the time of day or ambient light levels. Second, centralized control of multiple street and transport lights is becoming more common. ""Eventually you are going to have every single light fitting monitored, you will know how it is working and when it is not working; everything will be centralized,"" according to one rail operator. Read more LED components market in Japan to grow at CAGR of 9.3% to 2019 Semiconductor Today

The LED components market in Japan is rising at a compound annual growth rate (CAGR) of 9.3% during 2014-2019, according to the report 'LED Components Market in Japan 2015-2019' from market research firm Technavio. The Asia-Pacific region (APAC) is the major producer of LED components and is home to the four main manufacturing countries: Japan, Taiwan, China and South Korea (which account for an 83% share of the market). Vendors are continuously enhancing lighting technology for LEDs to compete with organic light-emitting diodes (OLEDs). This advance in lighting should enable manufacturers to increase the efficiency and durability of LED components. The advance will also aid features such as voltage, consumption, and conductivity in the end-products. For example, the average luminous efficiency of high-end products is about 150lm/W. Vendors from other regions have produced more than 170lm/W, but components in Japan are slowly spanning the defined range, leading to steady growth in the market. Since LEDs are energy saving and contain features that enhance sustainability, the Japanese government has proposed policy incentives to accelerate LED product promotion and encourage the use of LED lighting products, notes the report. The government has rolled out national policies to provide tax breaks to small- and medium-size enterprises (SMEs) on the purchase of energy-saving products, leading to growing margins for manufacturers. Also, many local governments (including Tokyo and Chiyoda) have launched subsidy programs wherein companies purchasing energy-saving products in accordance with the

specified standards can apply for grants to install one-fifth of the amount. Further, rising competition from countries such as China is one of the major challenges faced by vendors in the LED component market in Japan, says the report. Key vendors covered include Epistar, Everlight Electronics, Huga Optotech, and Lite-On Optoelectronics. Other prominent vendors include Kingbright Electronics, Lextar Electronics, Opto Tech, Taiwan Semiconductor Manufacturing Co (TSMC), and Techcore. Read more GaN devices market growing at CAGR of 15.1% from $481.8m in 2014 to $1315m in 2021 Semiconductor Today

The global gallium nitride (GaN) industrial devices market is rising at a compound annual growth rate (CAGR) of 15.1% from $481.8m in 2014 to $1315m in 2021, forecasts Transparency Market Research in its report 'GaN Industrial Devices Market - Global Industry Analysis, Size, Share, Growth, Trends and Forecast 2015 – 2021'. By volume, the market is expected to grow at a CAGR of 17.5% from 1099.6 million units in 2014 to 3427.2 million units by 2021. The report divides the GaN industrial devices market by type into two segments: power devices and optoelectronics. By revenue, optoelectronics was the largest contributor in 2014, accounting for 78% of the overall market, driven by the widespread implementation of these devices in light-emitting diodes and laser diodes. By application, the report classifies the GaN industrial devices market into three sub-segments: radio frequency (RF), light-emitting diodes (LEDs) and power devices. The LED segment was the largest contributor, both in terms of value and volume in 2014, accounting for market shares of 68% and 82.5%, respectively, due to the extensive usage of GaN-based LED devices in traffic signal lamps, vehicle lamps and liquid-crystal displays (LCDs) among others. Moreover, there have been two major developments in GaN-based LED technology: GaN-based devices on foreign substrates and LEDs based on bulk GaN substrates. The GaN high-electron-mobility transistor (HEMT) market is divided into seven segments: WiMAX/LTE, wireless phone infrastructure base

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transceiver station (BTS), CATV, V-SAT, satellite, defense, and others. By revenue, the wireless phone infrastructure BTS segment was the largest contributor in 2014, accounting for a market share of 26%. Rising adoption of GaN HEMT technology is leading to an increase in the number of base transceiver station installations, notes the report. In terms of value, North America accounted for the largest share of the global market in 2014 in terms of revenue (31.1%), due mainly to the high penetration of GaN-based transistors into military and defense applications. The penetration of GaN industrial devices is fueled by increasing demand for LEDs in computers, laptops, mobile tablets, gaming devices and televisions, notes the report. Europe accounted for the second largest market share (28.9%). Read more Cree's quarterly LED product revenue falls 21% amidst restructuring Semiconductor Today

For full-year fiscal 2015 (ended 28 June), Cree Inc of Durham, NC, USA has reported revenue of $1.63bn, down just 1% on fiscal 2014's record $1.65bn. Specifically, revenue for Lighting Products (mainly LED lighting systems and bulbs) grew 28% from $706.4m (43% of total revenue) in fiscal 2014 to $906.5m (55% of total revenue), driven by commercial lighting growing 37% while consumer lighting grew just 2%. This was offset by revenue for LED Products (LED components, LED chips, and silicon carbide materials) falling 28% from $833.7m (51% of total revenue) to $602m (37% of total revenue). Power & RF Product revenue grew 15% from $107.5m (6% of total revenue) to $124m (8% of total revenue), driven by Power products.

For fiscal fourth-quarter 2015, revenue was $382.2m (well below the $420-440m forecast given in April, but slightly above 24 June's revision to $375m). This is down 12% on $436.3m a year ago and 7% on $409.5m last quarter. Specifically, Power & RF Product revenue was steady at $30.8m (8% of total revenue). Lighting Product revenue was $229m (60% of total revenue), up 2% on $224m last quarter (55% of total revenue) –

driven by double-digit growth in commercial lighting – and up 10% on $208.4m (just 48% of total revenue) a year ago. However, this was mostly offset by a larger-than-expected seasonal decline in LED Product revenue to $122.2m (32% of total revenue), down 21% on $154.4m (38% of total revenue) last quarter – due primarily to lower consumer bulk sales, higher-than-expected erosion of LED average selling prices (ASPs), and Cree's restructuring (which reduced available LED fab capacity by about 40% during fiscal Q4) – and down 39% on $199.5m (as much as 46% of total revenue) a year ago. On 24 June, in order to improve cost structure, Cree announced a restructuring of its LED business to reduce excess capacity and overhead (by consolidating two fabs in Durham into one, taking till the end of the December quarter). The firm is also increasing LED reserves to reflect the more aggressive pricing environment during the quarter, and to factor in a more conservative pricing outlook for fiscal 2016. During the quarter, Cree hence recognized $84m of restructuring charges ($27m of LED revenue reserves, $11m of LED inventory reserves, and $46m of factory capacity and overhead cost reductions). […] Cree now targets total restructuring cost to be $102m, including $18m of additional charges in the first and second quarters of fiscal 2016 as it completes the consolidation of its LED factories. "Primarily related to additional capacity and overhead cost reduction identified during the factory consolidation process, we're finding the estimated fair values on certain equipment being held for sale," says chief financial officer Michael McDevitt. For fiscal 2016, Cree aims for revenue growth of 10% to $1.8bn (with growth driven by commercial lighting, compensating for consumer lighting being flat to slightly down), with operating margin of 8%. The firm targets property, plant & equipment (PP&E) spending to be lower than fiscal 2015, at $150m (primarily in first-half fiscal 2016), in order to complete certain existing infrastructural projects and to provide Lighting and Power & RF with incremental capacity. Free cash flow is targeted to be $85m (more in the second half of fiscal 2016 than the first half). Finally, Cree's board

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of directors has approved a $500m stock buyback program for fiscal year 2016. Read more Cree and Epistar sign global nitride LED chip patent cross-license agreement Semiconductor Today

Cree Inc of Durham, NC, USA and Taiwan's Epistar Corp (the world's largest manufacturer of LED epiwafers and chips) have signed a worldwide patent cross-license agreement for LED chips to further advance the growth of the LED lighting and LED bulb markets. Cree and Epistar both hold broad and substantial LED chip patent portfolios that are important for making blue LEDs (the foundation of white LEDs). Under the terms of the agreement, each party receives a license to the other's nitride LED chip patents and is granted certain rights to non-nitride LED chip patents. Over the term of the agreement, Cree will receive a licensing fee and royalty payments from Epistar. No technology transfer between the parties was included in the agreement. "This agreement underscores both companies' commitment to accelerating the adoption of LED lighting while respecting the value and importance of international intellectual property laws," says Cree's chairman & CEO Chuck Swoboda. "The patent license agreement we have achieved will help us to accelerate the R&D activities for creating new innovation," comments Epistar's chairman BJ Lee. "In addition, it is a clear indication of the strength of our LED chip patent portfolio and our desire to further the growth of the LED lighting market," he adds. "By entering into this cross-license agreement with Cree, Epistar is able to provide LED chips that ultimately benefit our customers across the world. Read more Feit Electric files LED patent infringement lawsuit against Cree Semiconductor Today

Feit Electric Company Inc of Pico Rivera, CA, USA has filed a complaint in the United States District Court for the Middle District of North Carolina alleging that the 4Flow line of LED light bulbs of LED maker Cree Inc of Durham, NC, USA infringes US Patent Nos. 8,408,748 and 9,016,901.

"Feit Electric Company fully supports competition in the market but competition by patent infringement is not acceptable," states president Aaron Feit. "Our company invests in LED lighting technology and we are building a patent portfolio to protect our position in the market. The action commenced today against Cree is simply that strategy put into action," he adds. Feit Electric has been "building a patent portfolio organically in conjunction with product development and through opportunistic acquisitions," says executive VP Alan Feit. In the action, Feit Electric is seeking an injunction against sales of Cree's 4Flow LED light bulbs as well as damages for past infringing sales. Previously, in January, Cree filed complaints with the US International Trade Commission (ITC) and the US District Court for the Western District of Wisconsin against Feit Electric and its Asian supplier Unity Opto Technology Co Ltd alleging infringement of 10 patents related to LED lighting and to address what was claimed to be Feit's false and misleading advertising claims that certain of its products meet ENERGY STAR specifications. Cree requested that the ITC issues an order to exclude infringing and falsely advertised articles from entry into the USA, and a cease and desist order requiring the respondents to cease selling infringing and falsely advertised LED bulbs in the USA. In February, the ITC agreed to open an investigation into unfair trade practices that includes Cree's allegations of infringement of eight of its US patents related to LED lighting. Read more Plessey wins AMSCI UK grant to support transition to 8" GaN-on-Si production Semiconductor Today

UK-based Plessey Semiconductors is to lead a £1.3m UK government-funded project in conjunction with Aixtron Ltd (the UK subsidiary of deposition equipment maker Aixtron SE of Herzogenrath, near Aachen, Germany) and Bruker Nano Surfaces Division (which has an office in Coventry, UK). The project will accelerate high-volume manufacturing of Plessey's LEDs created with GaN-on-silicon technology at its manufacturing site in Roborough, Devon. In accordance with an announcement on 26 March from the Department for Business,

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Innovation and Skills, 20 supply chain projects from across the UK will benefit from a total of £67m of government investment in relation to the Advanced Manufacturing Supply Chain Initiative (AMSCI), a funding competition designed to improve the global competitiveness of UK advanced manufacturing supply chains and encourage major new suppliers to locate in the UK. In addition, £109m is being invested in the same projects by industry. Specifically, Plessey Semiconductors is receiving a grant of £1m as part of the £1.3m project with Aixtron Ltd and Bruker Nano Services. The project should create up to 55 jobs and safeguard 2 jobs. "This project supports the work we have ongoing with Aixtron and Bruker to further increase the yield of our GaN-on-silicon process," says Plessey's chief technology officer Dr Keith Strickland. "These improvements are required as part of our move to 200mm (8-inch) silicon substrates," he adds. "A 200mm (8-inch) wafer has almost twice the usable area of our existing 150mm (6-inch) wafers and therefore will almost double the number of LEDs produced for the same relative cost." Read more Plessey expands dotLED range for wearables CSP versions Semiconductor Today

UK-based Plessey has expanded its dotLED range (designed specifically for wearable applications) with a wider selection of colors, including red, green and blue. The extremely small LED die have a footprint of only 0.2mm x 0.2mm, suiting low-profile electronic wearable applications.

Picture: Plessey's CSP-300 dotLED blue.

"We continue to win designs in the growing market for wearables and are now producing millions of LEDs every month," says VP of sales Giuliano Cassataro. "Our dotLED product range addresses the optical, mechanical and cost requirements for the typical wearable applications. These include wristbands trackers for health and fitness as well as many other applications for dot matrix displays," he adds. The white dotLED is available in a 1005 SMT package (1.0mm x 0.5mm) - a standard electronic component size easily handled by standard surface-mount machines used in high-volume, consumer electronics manufacturing. Delivering up to 1.0lm of white light with a 130 degree viewing angle from a 5mA drive current, the PLW13D003 meets the demand for ever smaller displays, says the firm. A blue version (the PLB13D003) is also available in a variety of wavelengths from 460nm to 480nm. "The increasing popularity of our dotLEDs has led us to develop our first chip-scale package (CSP) solution around the fit and performance of this product range," says chief technology officer Dr Keith Strickland. "Samples for this even smaller form factor will be available September this year in a selection of temperatures and colours." Read more Plessey launches range of LED filaments using GaN-on-Si die Semiconductor Today

UK-based Plessey has launched its range of LED filaments, manufactured with the firm's MaGIC (Manufactured on GaN-on-Si I/C) gallium nitride on silicon LEDs. The filaments are designed for the surging filament bulb market, where these replacement lamps have far better performance but still maintain the physical appearance of incandescent lamps. Plessey says that its chip-on-board (COB) LED filaments create the same amount of light while consuming less energy and offering longer life than a traditional tungsten incandescent light bulb.

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Picture: Plessey's LED filaments.

Picture: An LED filament bulb.

The LED filaments are designed with unique terminations so that they can be handled and spot welded by existing high-volume fully automated glass lamp manufacturing lines. In addition, Plessey has incorporated a bespoke approach to controlling the current and forward voltage (Vf) of the filaments when they are driven in a bridge configuration. "We have taken our existing chip-scale packaging [CSP] technology, also used for our dotLEDs, into a revised format for the filament," says chief technology officer Dr Keith Strickland. "Not only do we have an improvement in terms of manufacturability with GaN-on-silicon and enhanced the power control for filament resistors, but Plessey will also be incorporating other active and passive electronic components for chip-on-board and chip-scale packaging solutions in the next generation of filaments," he adds. "Thermal performance and customization are key to our filament product portfolio, and Plessey remains committed to bring to market unique LED products through our integrated approach to solid-state lighting applications." The PLF series of filaments come in a variety of lengths, light output and correlated color

temperatures (CCT), from very warm 2200K to 6500K. Read more Plessey releases range of GaN-on-Si blue LED die Semiconductor Today

UK-based Plessey has announced the release of its range of MaGIC (Manufactured on GaN-on-Si I/C) LED die, manufactured on the company's patented GaN-on-silicon technology. The blue die (sometimes referred to as blue pump for their ability to pump phosphor to a white colour range) are the latest innovation in high brightness LED die designed for a wide range of medium to high power applications including general lighting, signage, commercial, residential and street lighting.

Picture: Plessey's 4.5mm high-power LED die.

"We have developed a wide range of LED die for a number of applications and our GaN-on-silicon technology works particularly well in higher-power applications such as high-bay, street lights, projector lamps, spot lamps and floodlighting," says chief technology officer Dr Keith Strickland. "his current process technology will become the base for our application-specific LEDs, the ASLED, which bridges the gap between LED component suppliers, solid-state lighting fixture designers and the OEMs." The manufacturing process produces a vertical LED structure that has the anode as bottom contact and the cathode formed in the top metal layer. The layout of the top metal layer is optimized for a particular LED size and die

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operating current, and includes one or more bond pads for connecting to the cathode. "We are seeing a definite move away from discrete PLCC designs, especially in the higher-power applications," notes Giuliano Cassataro, VP global sales. "By having our own growth and semiconductor processing facility in Plymouth, Plessey provides the flexibility and speed of response required for a vast range of high-end applications that can use the thermal and light output from our silicon LED die," he adds.

Picture: Plessey's 1mm die for 350mA.

Plessey is offering its range of blue die in various wavelength options. Capable of a light output efficiency (wall-plug efficiency, WPE) of over 60%, the die are supplied to a standard thickness of 150μm (although other thicknesses can be supplied, down to a minimum of 75μm). The die are supplied on a blue tape in single intensity and colour bins to provide close uniformity, and are intended to be used with standard pick & place machines. Samples are available in a variety of die pack formats with blue die wavelengths ranging from 420nm to 480nm and from 1mW to 10W, with the PExS4500 range having a typical optical output power of 4000mW from a 3A drive current. Read more Plessey retrofits its manufacturing facility with MaGIC LED kits Semiconductor Today

Plessey says that it is retrofitting its manufacturing facility in Plymouth, UK with LED modules designed using its MaGIC (Manufactured on GaN-

on-Si I/C) GaN-on-silicon LEDs. The retrofit involves replacing aging fluorescent tubes and compact fluorescent bulbs in existing fixtures to use new LED light modules produced in the same facility. The manufacturing site currently has about 2700 fixtures with 4200 fluorescent lamps that consume 1,000,000kW/h of electricity at a cost of £100,000 a year and costs about £5000 in materials and 200 man hours a year to maintain. After the retrofit is completed, the firm expects to see a 25-40% reduction in electricity consumption, saving tens of thousands of pounds per year. Lighting solutions using LED technology are over 50% more efficient that their fluorescent and compact fluorescent (CFL) counterparts, notes the firm. LED lights can be dimmed, have higher-quality colour control and do not use highly toxic mercury. LED lights also have much longer working life expectancy than any other forms of artificial lighting, lasting up to 100,000 hours compared with 10,000 hours for fluorescent tubes and 1000 hours for tungsten filament light bulbs. Market research firm Strategies Unlimited's new 2015 report projects a global LED-retrofit-lamp market exceeding $3.7bn by 2016. The growth in solid-state lighting (SSL) products intended for existing sockets is from a $2.2bn base in 2011, and the report projects annual 30% growth in the number of units sold. Read more Transfer of ALLOS' 150 and 200mm GaN-on-Si epi technology to Epistar concluded in under 6 months Semiconductor Today

Technology engineering & licensing firm ALLOS Semiconductors GmbH of Dresden, Germany have concluded its joint project to establish its mature 150 and 200mm gallium nitride on silicon (GaN-on-Si) technology at Epistar Corp of Hsinchu Science Park, Taiwan (the world's largest manufacturer of LED epiwafers and chips). The project was executed with better-than-expected results and ahead of schedule in less than six months. For example, reproducible crystal quality was achieved with a total dislocation density of 2×108cm2. It is reckoned that, with this performance, Epistar has caught up with the world-leading results of forerunners that have

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been developing GaN-on-Si LED technology for some time. During the project ALLOS established its GaN-on-Si epiwafer process on Epistar's epitaxial reactors. Epistar engineers were trained and worked in the integrated project team with ALLOS to gain full understanding and control over the GaN-on-Si technology. Currently, Epistar's own LED technology is being transferred to GaN-on-Si structures. "To conduct the technology transfer with ALLOS has proven to be the right decision for Epistar as it allowed us to quickly gain command over their leading GaN-on-Si technology in a very cost-efficient and reliable way," comments Epistar's president Dr M. J. Jou. "In a second phase we will now be focussing on realising the cost advantages of GaN-on-Si LEDs and to unlock the application benefits," he adds. "To accomplish a project of this size and complexity with such results is a complete success," comments ALLOS' CEO & co-founder Burkhard Slischka. "This result underlines ALLOS' project execution skills as well as our technical capabilities to grow crack-free wafers with market-leading crystal quality," he claims. "This is an example that our fast, cost-effective and successful implementation of GaN-on-Si helps our customers to reduce development risk and to save time and money." Read more Bridgelux to be acquired by group led by China Electronics Corporation Semiconductor Today

Bridgelux Inc of Livermore, CA, USA has agreed to be acquired by an investment group led by China Electronics Corporation (CEC) and ChongQing Linkong Development Investment Company. Established in 1989, CEC is one of China's largest IT firms, controling 61 second-level subsidiaries including 13 listed holding companies employing more than 70,000 staff at manufacturing facilities in Beijing, Shanghai, Wuhan, Shenzhen, Nanjing, Changsha, and Xiamen. Bridgelux is a developer and manufacturer of solid-state lighting sources with more than 145 staff. Last year it announced an expansion of its China operations, increasing its investment and capabilities in the country by opening an R&D

center in Xiamen dedicated to supporting the development and manufacture of new solid-state lighting products - including extensions to its V Series chip-on-board (COB) product line – and opening an applications lab in Shanghai's Hongqiao district to assist China customers with the design and enhancement of lamps and fixtures integrating Bridgelux's LED light source products. Bridgelux's Xiamen R&D facility is co-located with China-based LED and solid-state lighting (SSL) company Kaistar Lighting (which was jointly founded by CEC and Epistar), a strategic supply chain partner that provides outsourced contract manufacturing of LEDs to Bridgelux and invested in the firm in 2012. Previously, in 2013, Bridgelux transferred its gallium nitride-on-silicon (GaN-on-Si) technology assets to Toshiba and inaugurated a new phase in their GaN-on-Si LED collaboration (including an expanded licensing and manufacturing supply relationship), while Bridgelux continued to develop and market its GaN-on-sapphire LED products as a fabless solid-state lighting company. "The advances Bridgelux has made over the last 13 years have been instrumental in driving the adoption of energy-efficient LED technologies worldwide," comments CEC's CEO Mr Liu. "Bridgelux has all of the characteristics we look for in an investment, including leading technology, a broad IP portfolio and a globally recognizable brand and channel," he adds. "This investment is an important step toward further aligning CEC and partner assets into a coordinated supply chain built to serve the unique requirements of the solid-state lighting market." With its existing investments in lighting fixture and lamp manufacturing as well as other IT and consumer electronics technologies, CEC's captive businesses are expected to offer substantial scale and growth benefits for Bridgelux. Also, CEC and its affiliates have built technology development and manufacturing operations across the LED supply chain. Bridgelux reckons that alignment with these partners should give it a durable, long-term cost advantage, complementing its existing technology, and will further allow it to focus on segment- and application-level innovations. Read more

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Seren Photonics wins UK Royal Society's Emerging Technologies award Semiconductor Today

As one of 30 finalists at the UK Royal Society of Chemistry's Emerging Technologies Competition 2015 in London on 29 June, Seren Photonics Ltd of Pencoed Technology Park, UK was awarded third place in the 'Materials' category for its innovation in semi-polar gallium nitride (GaN) templates for next-generation LEDs. Presenters from across Europe went head-to-head to pitch their ideas for the latest healthcare, energy and sustainability, and materials technologies to panels of industry experts. The competition, which is in its third year, included small companies and academic entrepreneurs from nine countries outside the UK for the first time, including Denmark, Germany, Switzerland and The Netherlands. Seren's technology and business strategy, presented by chief development officer Dr Bedwyr Humphreys, emphasized the benefits of semi-polar GaN in enhancing the performance of existing LEDs, enabling accelerated adoption in automotive and general lighting applications. Spun off from the University of Sheffield in 2009 with funding from venture capital firm FusionIP plc (now part of IPGroup plc), Seren Photonics has commercialized technology developed by professor Tao Wang of the Electronic and Electrical Engineering Department and uses nano-engineered structures to enhance the properties of III-nitride materials. Read more HexaTech wins continued DoE funding Semiconductor Today

HexaTech Inc of Morrisville, NC, USA, which manufactures aluminium nitride (AlN) substrates and is developing long-life UV-C LEDs and high-voltage power devices, has received a continuation of funding under the US Department of Energy's Advanced Research Projects Agency (ARPA-E) development program. The cost-share extension is valued at $1.2m over one year, and follows $2.8m over two years when the contract was initiated in 2012. HexaTech's contract focuses on developing high-power semiconductor switching devices based on AlN to more efficiently control the flow of

electricity across high-voltage electrical lines. AlN-based devices should exceed the capabilities of existing materials, enabling smaller, more reliable components. Further implementation of these components could decrease the cost of electricity transmission while increasing overall grid security and reliability, it is reckoned. "This contract extension will allow us to further expand our market leadership in high-power AlN device development," says CEO John Goehrke. "Combined with ARPA-E's unique Tech-To-Market concept, we anticipate not only raising the bar in device performance, but also raising awareness for AlN in general, which will in turn be a significant growth opportunity for our core substrate business," he adds. "This continued support from ARPA-E will allow us to demonstrate the potential of AlN for high-voltage devices by optimizing MOCVD [metal-organic chemical vapor deposition] growth parameters, as well as fabricating and testing commercially oriented components," says Dr Baxter Moody, principal investigator for the program at HexaTech. Read more Asahi Kasei orders Aixtron CCS MOCVD system to start commercial production of DUV LEDs Semiconductor Today

Equipment maker Aixtron SE of Herzogenrath, near Aachen, Germany says that Tokyo-based chemical company Asahi Kasei has ordered a Close Coupled Showerhead system (CCS) metal-organic chemical vapor deposition (MOCVD) system, for delivery in third-quarter 2015, for pilot production of deep ultraviolet (DUV) LEDs based on aluminium gallium nitride (AlGaN).

Picture: Aixtron's Close Coupled Showerhead system, in 6x2''-wafer configuration.

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Aixtron says that Asahi Kasei's decision to purchase a Showerhead reactor for DUV LED production is based on the positive experience with a previous MOCVD tool already in operation. It chose Aixtron's proven CCS technology again as it enables the optimization of the chamber geometry for both high- and low-pressure regimes by the additional dynamic chamber height adjustment. Read more Crystal IS launches Optan SMD UVC LED for sensor and instrumentation makers Semiconductor Today

Crystal IS Inc of Green Island, NY, USA, an Asahi Kasei company that makes proprietary ultraviolet light-emitting diodes (UVC LEDs) grown pseudomorphically (strained) on aluminum nitride (AlN) substrates, has launched its latest Optan UVC LED product. Operating from a maximum drive current of 300mA in continuous mode, the Optan SMD (surface-mount device) UVC LED emits at wavelengths of 260-275nm over a wide viewing angle of 100° with light output of more than 2mW. The typical L50 life-time is 3000 hours at 100mA. Targeted at manufacturers of sensors and instrumentation in ocean and industrial process applications (for which performance and reliablity are critical), the Optan SMD is a long-life solution with low power consumption, giving users an increase in intervals for instrument maintanence. Optan SMD is environmentally friendly, which is essential for the control of damage from bacteria and biofilms (which has a wide-ranging impact across industries that is estimated to cost several hundred billion dollars annually). However, solutions available currently are either not completely effective or being phased out due to toxicity concerns. ""Our customers came to us with a difficult situation in controlling biofouling, where coatings, traditional UV lamps or mechanical wipers weren't that effective,"" says CEO Larry Felton. ""Our latest Optan product will solve that problem, especially when it comes to ocean and industrial process instrumentation."" Crystal IS says that the Optan SMD enables more effective and efficient biofilm and biofouling control. The Optan SMD also supports total organic carbon (TOC) monitoring in water (since high levels of

TOC can degrade industrial water purification systems, reducing semiconductor yields, contaminating pharmaceutical batches and damaging power and steam generation equipment). In addition, the Optan SMD can be used as a low-voltage source of UVC light for the calibration of cameras, photodetectors, etc. Samples of the Optan SMD are available now. Read more

ELECTRONICS

GaN technology and the potential for EMI EDN Network

While attending DesignCon 2015 last January, I had the chance to hear an interesting keynote presentation by Alex Lidow, CEO of Efficient Power Conversion, Inc., speak on the upcoming development in gallium nitride (GaN) technology for high-power switching devices. I also had the fortune of meeting Steve Sandler, author of the book, Power Integrity - Measuring, Optimizing, and Troubleshooting Power Related Parameters in Electronic Systems, who was associated with measuring the picosecond edge speeds of these devices (see his article in the References section). Because of the fast switching speeds and related higher efficiencies of these new power switches, we’ll expect to see them primarily applied to switch-mode power supplies and RF power amplifiers. They may broadly replace existing MOSFETs and have lower “on” resistance, less parasitic capacitance, are smaller, and faster. I’m already noticing new products using these devices. Other applications include telecom DC-DC, wireless power, LiDAR, and class D audio. Obviously, any semiconductor device that switches in a few picoseconds is likely to generate large amounts of EMI. In order to evaluate these GaN devices, Sandler arranged for me to test some evaluation boards. The one I chose to characterize was a half-bridge 1 MHz DC-to-DC buck converter from Efficient Power Conversion (EPC9101, Figure 1). Refer to the References section for additional information on this demo board, plus several others.

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Figure 1 - The demo board used to characterize GaN EMI. The GaN device is circled and I’ll be measuring the switched waveform on the left end of L1.

The demo board takes 8 to 19 volts and converts it to 1.2 volts at 20 amps (Figure 2). I ran it at 10 volts with a 10-Ω, 2-W load resistor.

Figure 2 - The block diagram of the half-bridge DC-DC converter. The waveforms were measured at the left end of L1 to return.

I tried to capture the edge speed by using a 1.5 GHz single-ended probe (R&S RT-ZS20, Figure 3) and probing at the switched end of L1, but the equipment available had too limited a bandwidth to capture it faithfully. The best I was able to capture (Figure 4) was a 1.5 ns rise time (which, from an EMI point of view, is pretty fast to begin with!). To accurately record the typical 300 to 500 picosecond edge speed would require an oscilloscope of 30 GHz bandwidth, or more. For more on measuring the switching speed, refer to the article by Sandler in the References at the end of this article.

Figure 3 - Measuring the leading edge using a Rohde & Schwarz RTE1104 oscilloscope and RT-ZS20 1.5 GHz single-ended probe.

Figure 4 - The captured rise time showing ringing at 217 MHz. The fastest edge speed indicated was 1.5 ns, but in reality, the measurement was bandwidth-limited.

Read more Can SiC and GaN Become a Player in the Automotive Market? Electronics 360

Wide-band gap semiconductors based on SiC and GaN have been in the market for more than five years now, but recently, interest has increased for automotive applications as Hybrid Electric Vehicles/Electric Vehicles (HEV/EV) have become more prevalent. Components based on this technology are more efficient than conventional silicon-based components, and can reduce system cost by as much as 6% and system size by up to 50%. All this is great news for OEMs in the battle to lose weight. Toyota, the pioneer of electrification, is already testing SiC components in the powertrain of its Camry HEV.

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At the semiconductor level, traditional power IC suppliers such as Cree, Rohm, NXP/Freescale, Microsemi, Infineon, and ON Semiconductor are investing in these technologies. Read more SiC market to treble and GaN to explode - if challenges are overcome Semiconductor Today

According to the report 'GaN and SiC for power electronics applications' from Yole Développement, in 2014 the silicon carbide (SiC) chip business was worth more than $133m, with power factor correction (PFC) and photovoltaics (PV) still the leading applications (as in previous years). More than 80% of this market consists of SiC diodes, which in 2020 will remain the main contributor across various applications, including electric vehicles and hybrid electric vehicles (EV/HEV), PV, PFC, wind, uninterruptible power supplies (UPS) and motor drives, reckons Yole. SiC transistors will grow in parallel with diodes, driven by PV inverters, forecasts the report. However, challenges must be overcome prior to the adoption of pure SiC solutions for EV power train inverters, which is nevertheless expected by 2020. Including the growth in both diodes and transistors, Yole expects the total SiC market to more than treble $436m by 2020. Gallium nitride (GaN) potentially has a huge total accessible market (TAM), and its adoption would therefore be significant, says Yole. However, the starting point and the growth rate are directly linked to two important questions:

•How will the emerging applications of low-voltage GaN expand, and how will GaN be adopted by these applications? •Will 600V devices make their way to market?

Yole has integrated these variables in developing two scenarios for the GaN device market up to 2020. The analysis is based on the penetration rate of GaN in different applications including DC-DC conversion, Lidar, envelope tracking, wireless power, and PFC. The firm hence estimates that by 2020 the GaN device market will grow to $303m in the nominal scenario, or $560m in the accelerated scenario (where low-voltage GaN and 600V GaN are rapidly adopted).

Emerging applications (namely envelope tracking, wireless power and Lidar) will collectively consume one third of GaN transistors, it is forecast. In both scenarios, low-voltage applications below 200V are expected to be the major contributors to the market. Companies moving in right direction to overcome remaining technical challenges Designing a totally new product with these semiconductor materials will induce R&D expenses that must be compensated by adding value at the system level, says Yole. This could include improving cost, size, and operating conditions compared with regular silicon solutions. To capture this added value, an integrator must get the full benefit from the increased operating frequency and temperature of wide-bandgap (WBG) devices. So far, the WBG market has not grown as fast as hoped. The four barriers to device adoption remain: high cost at the device level; reliability; multi-sourcing; and integration. Many R&D programs have been launched in recent years. Some prototypes have demonstrated that the bill of materials (BOM) cost can be lower at the system level when using WBG devices. To overcome reliability challenges, Rohm and Cree have announced new SiC device generations or platforms with enhanced, more stable specifications. SiC and GaN devices are also going through reliability tests to reduce the risk involved in adoption. Many companies - including Cree, Rohm, ST Microelectronics, Mitsubishi and GE - have now developed SiC MOSFETs. So, end-users are more able to multi-source these devices. By contrast,

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there is a limited number of suppliers in the GaN market. In the coming years, new entrants such as ExaGaN and TSMC should provide extra sourcing options. Also, Infineon and Panasonic have announced this year that they will establish a dual-sourcing relationship for normally-off 600V GaN power devices. Integrating these fast-switching, high-operating-temperature devices remains one of the major challenges. WBG suppliers and end-users need to reconsider many factors, including device packaging, module packaging, gate driver integration and topology design.

Packaging is becoming a particular bottleneck, but the good news is that companies are moving in the right direction, says Yole. GaN device makers EPC and GaN Systems have both adopted advanced packaging, which seems to be more suitable than traditional power device packages. The recent acquisition of APEI by Cree should likewise accelerate the development of SiC module packaging. Recent financial moves indicate market confidence in WBG devices There have recently been several pieces of good news for the WBG sector, says Yole. The existing SiC device market leader Cree has decided to spin off its Power and RF division as a separate company, and will issue shares in a new IPO. Yole interprets this as a positive sign of the continuing growth in the SiC power device market. At the same time, about $100m in investment has been made in various GaN startups. Two of them are in the top four commercial GaN companies. In May, GaN Systems raised $20m in venture funding. In June, Exagan raised €5.7m ($6.5m) in

first-round financing to produce high-efficiency GaN-on-silicon power-switching devices on 200mm wafers. Also, Transphorm announced a new $70m funding round led by investment firm KKR. These investments reflect the confidence in the GaN device market and investors' willingness to provide funds to accelerate production capabilities, says Yole. Will GaN and SiC compete for the same power electronics applications? After years of discussion about whether it would be GaN or SiC, the answer is now clearer than ever, states Yole. SiC diodes have been on the market for over 14 years, and are becoming a mature technology, leaving no room for GaN diodes. GaN transistors have made their way into low-voltage applications, which SiC will find difficult to challenge. Commercial SiC transistors exist in the 600-3300V range. Compared to GaN lateral devices, their advantages at voltages over 1200V are now widely recognized. In early 2015, SiC device leader Cree launched its 900V platform. This is considered by the market as a significant move for SiC, signaling its intention to address 900V and lower voltage applications. GaN is also trying to enter the 600V market. Applications such as PFC, on-board chargers, and low-voltage/high-voltage DC-DC converters for automotive applications will therefore be the main battlefields for GaN and SiC in the coming years, reckons Yole.

In the end, integrators do not care what the chips they buy are made of, notes the market research firm. They want suitable devices at reasonable

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prices to make a system desired by the market. The real competition is not between GaN and SiC, but WBG versus incumbent silicon-based technology. Silicon insulated-gate bipolar transistor (IGBT) technology is progressing, becoming better and cheaper. However, in the future, the market will not be as dominated by silicon-based devices as it is today, but more diversified. A variety of devices - including silicon, GaN, SiC and others that are yet to be developed - will find their own niches, concludes Yole. Read more Imec extends GaN-on-Si R&D initiative for joint research on 200mm epi and E-mode device Semiconductor Today

Nano-electronics research center Imec of Leuven, Belgium is extending its gallium nitride-on-silicon (GaN-on-Si) R&D program, and is now offering joint research on GaN-on-Si 200mm epitaxy and enhancement-mode device technology. The extended R&D initiative includes exploration of novel substrates to improve the quality of the epitaxial layers, new isolation modules to increase the level of integration, and the development of advanced vertical devices. Imec says that it welcomes new partners interested in next-generation GaN technologies and companies looking for low-volume manufacturing of GaN-on-Si devices to enable the next generation of more efficient and compact power converters. GaN technology offers faster-switching power devices with higher breakdown voltage and lower on-resistance than silicon, making it an outstanding material for advanced power electronic components. Imec's R&D program on GaN-on-Si was launched to develop a GaN-on-Si process and bring GaN technology towards industrialization. "Since the program's launch in July 2009, we have benefited from strong industry engagement, including participation from integrated device manufacturers (IDMs), epi-vendors and equipment and material suppliers. This underscores the industrial relevance of our offering," says Rudi Cartuyvels, executive VP of smart systems at Imec. Building on its track record in GaN epilayer growth, new device concepts and CMOS device integration, Imec has now developed a complete

200mm CMOS-compatible GaN process line. Imec's GaN-on-Si technology is reaching maturity, and companies can gain access to the platform by joining its GaN-on-Si industrial affiliation program (IIAP). The process line is also open to fabless companies interested in low-volume production of GaN-on-Si devices tailored to their specific needs, through dedicated development projects. Imec's portfolio includes three types of buffers optimized for breakdown voltage and low trap-related phenomena (i.e. current dispersion): a step-graded aluminium gallium nitride (AlGaN) buffer, a superlattice buffer, and a buffer with low-temperature AlN interlayers. Imec explored side-by-side enhancement-mode power devices of the MISHEMT and p-GaN HEMT type, as well as a gate-edge-terminated Schottky power diode featuring low reverse leakage and low turn-on voltage. The latest generation of Imec enhancement-mode power devices shows a threshold voltage beyond +2V, an on-resistance below 10 ohm mm and output current beyond 450mA/mm. These devices represents the state-of-the-art of enhancement-mode power devices, Imec claims. In this next phase of the GaN program, Imec is focusing on further improving the performance and reliability of its existing power devices, while in parallel pushing the boundaries of the technology through innovation in substrate technology, higher levels of integration and exploration of novel device architectures. "Interested companies are invited to become a partner and actively participate in our program," says Cartuyvels. "Imec's open innovation model allows companies to have early access to next-generation devices and power electronics processes, equipment and technologies and speed up innovation at shared cost." Read more Cambridge Electronics launches GaN transistors and power electronic circuits Semiconductor Today

Cambridge Electronics Inc (CEI) – which was spun off from Massachusetts Institute of Technology (MIT) in 2012 – has announced a range of gallium nitride (GaN) transistors and power electronic circuits targeted at cutting energy usage in data

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centers, electric cars, and consumer devices by 10-20%. Power electronics is a ubiquitous technology used to convert electricity to higher or lower voltages and different currents — such as in a laptop's power adapter, or in electric substations that convert voltages and distribute electricity to consumers. Many of these systems rely on silicon transistors that switch on and off to regulate voltage but, due to speed and resistance constraints, waste energy as heat. CEI says that its GaN transistors have at least one-tenth the resistance of such silicon-based transistors, allowing much higher energy efficiency and orders-of-magnitude faster switching frequency, so that power electronics systems made with these components can be much smaller. CEI is using its transistors to enable power electronics that will make data centers less energy-intensive, electric cars cheaper and more powerful, and laptop power adapters one-third the size — or even small enough to fit inside the computer itself. CEI's co-founders and and co-inventors of the technology include Tomás Palacios (an MIT associate professor of electrical engineering and computer science); technical advisory board chair Anantha Chandrakasan (the Joseph F. and Nancy P. Keithley Professor in Electrical Engineering); VP for device development Dr Bin Lu; director of operations Dr Ling Xia; director of epitaxy Dr Mohamed Azize; and director of product reliability Dr Omair Saadat. Read more GaN Systems signs Shenzhen-based SZ APL as distribution partner in China and Taiwan Semiconductor Today

GaN Systems Inc of Ottawa, Ontario, Canada - a fabless producer of gallium nitride (GaN)-based power switching transistors based on its proprietary Island Technology for power conversion and control applications - has appointed Shenzhen APL to distribute its Island Technology high-power gallium nitride devices in China and Taiwan. With headquarters in Shenzhen and additional offices in Shanghai, Beijing and Taipei, SZ APL has extensive experience in power electronics components distribution to major tier-

1 customers in the automotive, industrial and enterprise segments. Read more EPC launches fast, small monolithic GaN power transistor half-bridge operating over 2MHz for Class-D audio Semiconductor Today

Efficient Power Conversion Corp (EPC) of El Segundo, CA, USA, which makes enhancement-mode gallium nitride on silicon (eGaN) power field-effect transistors (FETs) for power management applications, has launched the EPC2106, an e-mode monolithic GaN transistor half-bridge. By integrating two eGaN power FETs into a single device, interconnect inductances and the interstitial space needed on the PCB are eliminated. This increases both efficiency (especially at higher frequencies) and power density, while reducing assembly costs to the end-user's power conversion system, says the firm. The EPC2106 half-bridge component has a voltage rating of 100V with a typical RDS(on) of 55mΩ, output capacitance less than 600pF, zero reverse recovery (QRR), and a maximum pulsed drain current of 18A. The low on-resistance and capacitance of GaN enables high efficiency and significantly reduces distortion in Class-D systems. The EPC2106 comes in a very small 1.35mm x 1.35mm chip-scale package for improved switching speed and thermal performance for increased power density. Read more EPC launches low-cost, high-power-density eGaN FET for high-frequency power conversion including wireless power transfer Semiconductor Today

Efficient Power Conversion Corp (EPC) of El Segundo, CA, USA, which makes enhancement-mode gallium nitride on silicon (eGaN) power field-effect transistors (FETs) for power management applications, has launched the EPC2039 high-power-density eGaN power transistor. The EPC2039 is an extremely small 1.35mm x 1.35mm (1.82mm2) 80VDS, 6.8A power transistor with a maximum RDS(on) of 22mΩ with 5V applied to the gate. EPC says that the GaN power

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transistor delivers high performance in power conversion systems due to its high switching capabilities in a very small package. "It enables designers to increase the output power of their designs without increasing the space needed to do it," says Steve Colino, VP global sales & marketing. The EPC2039 is designed primarily for high-frequency power conversion applications, such as synchronous rectification, Class-D audio, high-voltage buck converters, wireless charging, and pulsed power (LiDAR) applications. Emerging LiDAR applications include driverless vehicles and augmented reality. Pricing for the EPC2039 power transistor is $0.78 each in 1000-unit quantities. Read more Qorvo's quarterly revenue grows 6% as mobile products growth outweighs 40% drop in wireless infrastructure Semiconductor Today

For fiscal first-quarter 2016 (ended 27 June 2015), Qorvo Inc, a provider of core technologies and RF solutions for mobile, infrastructure and aerospace/defense applications, has reported revenue of $673.6m, up 6% on $633.9m last quarter and up 23% on $547.1m a year ago for the combined revenues for the June 2014 quarter of RF Micro Devices Inc of Greensboro, NC and TriQuint Semiconductor Inc of Hillsboro, OR, USA (following the merger of the two firms on 1 January). There were two greater-than-10% customers (although the larger, at about 33% of revenue, represented the aggregated demand of multiple subcontractors for this end-customer). The second 10% customer was telecoms equipment maker Huawei Technologies Co Ltd of Shenzhen, China. Growth was led by Mobile Products revenue of $551m, up 12% on last quarter and 35% on a year ago as Qorvo continues to capture a broad array of opportunities supported by long-term trends. In particular, global demand for broad-based data continues to proliferate while front-end complexity and the performance requirements for RF solutions continue to expand. Despite having seen a slowing among handset customers in China, the country still comprised Qorvo's largest customer by region. ""Qorvo has secured excellent growth opportunities in China,"" notes president & CEO Bob Bruggeworth. For example,

during the quarter, Qorvo began shipments of RF Flex integrated front-end transmit and power-amplifier modules to leading China-based smartphone makers. The strength in Mobile Products was sufficient to offset a 13% drop in Infrastructure & Defense Products (IDP) revenue from $140m last quarter to $122m. This was driven wireless infrastructure – which had comprised about one-third of IDP revenue in the March quarter (i.e. about $45m) – falling sharply by 40% (to less than $25m), due primarily to a pause in LTE base-station deployments. Excluding wireless infrastructure, IDP revenue grew about 9% year-on-year, with sequential strength across all other markets. Gallium nitride (GaN)-related revenue grew 30% year-on-year, led by strength in both CATV and defense & aerospace markets, where Qorvo claims to be the GaN market leader (having released over 100 GaN products during the past 18 months in both high-power and high-frequency applications, offering what it says is the industry's broadest portfolio of GaN capabilities with advanced low-cost packaging techniques). During the quarter, Qorvo sampled GaN custom macrocell power amplifiers to major base-station customers. "We continue to see GaN as a disruptive technology, displacing silicon LDMOS," says Bruggeworth. On a non-GAAP basis, gross margin has risen from 44.8% a year ago (for RFMD and TriQuint combined) and the record 50.4% last quarter to 51.5%, reflecting favorable product mix and the realization of cost synergies. Read more Advantech's GaN-based SSPAs power 4K Ultra HDTV transmission of South America's soccer tournament Semiconductor Today

Advantech Wireless Inc of Montreal, Canada (which manufactures satellite, RF equipment and microwave systems), says that its gallium nitride (GaN)-based SapphireBlu Series solid-state power amplifiers (SSPAs) recently powered 4K Ultra HDTV transmission at the Copa América international soccer tournament between South American national teams that took place in June/July in Chile.

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Advantech claims that its SSPAs were selected for their higher performance and reliability combined with the smallest form factor and lowest power consumption on the market. ""With the new requirements of HDTV and Ultra HDTV, broadcasters need more power per feed,"" says VP business development Cristi Damian. ""The second-generation GaN-based SSPAs deliver the best solution for DSNG [digital satellite news gathering] applications in terms of performance, quality and overall cost of ownership,"" he claims. "Fleets of DSNG vehicles from our customers have been upgraded for full HDTV transmission capability in order to transmit uninterrupted feeds of these sports tournaments to all countries around the world." Advantech says that its second generation of GaN-based SapphireBlu SSPA/SSPB offers very high linearity in a compact single package. The systems are designed for Ultra HD transmission broadcasting and are DVB-S2X ready. The increased linearity comes at the same time with no additional increase in size, weight and energy consumption, the firm adds. Read more University of Arkansas receives $200,000 NSF grant to study GaN device modeling Semiconductor Today

The University of Arkansas' GRid-connected Advanced Power Electronic Systems Center (GRAPES) has received a $200,000 grant to study the modeling of gallium nitride (GaN) devices. Alan Mantooth, Distinguished Professor of electrical engineering and executive director of the center, will lead the effort. Researchers at the center work to accelerate the adoption and insertion of power electronics into the electric power grid. Improvements in these devices should ultimately lead to lower costs for consumers and a substantial reduction in carbon emissions. As a hard-compound, mechanically stable semiconductor material that has high heat capacity and thermal conductivity, GaN can be used to develop devices that can operate at higher voltages, temperatures and switching frequencies than those currently using silicon. One of the barriers to the acceptance of such new devices is a lack of high-quality models for circuit

simulation that allow designers to evaluate them against the entrenched silicon technology. Since the vast majority of all circuit design and simulation is performed in computer programs, the lack of these models makes it very difficult for circuit designers to accurately portray how GaN devices will behave, says University of Arkansas. The grant will allow the researchers at GRAPES to develop and evaluate a high-performance compact model for GaN power devices. Compact models are used by circuit designers to simulate the performance and behavior of their designs before committing them to manufacture. These models are especially important in power electronic applications where many real-world scenarios can be analyzed safely. Further, statistical and failure mode analyses, which are practically impossible through experimentation, can be easily performed, concludes the University of Arkansas. Read more MACOM showcasing fourth-generation GaN technology for RF energy applications at European Microwave Week Semiconductor Today

In booth #235 at European Microwave Week (EuMW 2015) at Palais Des Congres in Paris, France (6-11 September), M/A-COM Technology Solutions Inc of Lowell, MA, USA (which makes semiconductors, components and subassemblies for analog RF, microwave, millimeter-wave and photonic applications) is showcasing its gallium nitride (GaN) RF product and technology portfolio, including its Gen 4 GaN-on-silicon RF product solutions optimized for commercial, industrial, scientific & medical applications. At volume production levels, Gen 4 GaN technology is expected to yield devices that achieve breakthrough performance and higher efficiency below the semiconductor cost per watt of comparable LDMOS silicon products, and at significantly lower cost than comparably performing GaN-on-SiC (silicon carbide) wafers. As a member of the RF Energy Alliance, MACOM is bringing GaN RF technology into mainstream applications, including RF ignition systems, solid-state cooking and high-lumen plasma lighting. Read more

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OTHER

Monocrystal produces first 300kg Kyropoulous sapphire crystals Semiconductor Today

Using its proprietary modified Kyropoulos (KY) method, Monocrystal Inc of Stavropol, Russia, which manufactures large-diameter sapphire substrates and cores for LED, optical product and RFIC applications (as well as screen printing metallization pastes for silicon-based solar cells), has produced what is reckoned to be the world's first 300kg KY sapphire crystal.

Picture: Monocrystal's CEO Oleg Kachalov with 300kg Kyropoulous crystal.

"We are committed to helping our customers enable large-size sapphire applications in both LED and consumer electronics by growing extra-large sapphire crystals," says CEO Oleg Kachalov. "At the same time, larger crystals will drive sapphire cost down and open new price-sensitive markets to us," he adds. "Our 300kg crystals put Monocrystal production scalability to a revolutionary level and are vital for broader sapphire adoption in smartphones and other handsets, where glass is still the mainstream." Monocrystal has been developing sapphire crystal growing technology for more than 30 years, and 300kg crystal represents a milestone in expanding its capabilities in both capacity development and cost reduction. Read more

Riber reports first-half revenue up 18% year-on-year to €5.7m Semiconductor Today

Riber S.A. of Bezons, France, which manufactures molecular beam epitaxy (MBE) systems as well as evaporation sources and effusion cells, has reported an 18% rise in revenue from €4.8m in first-half 2014 to €5.7m in first-half 2015 (43% from Asia, 40% from Europe, 11% from Africa and 6% from North America). MBE Systems sales picked up again, doubling from just two research systems in first-half 2014 to four (with total MBE Systems revenue rising by 32% from €2.1m to €2.8m). Sales of services & accessories (€2.1m) and cells & sources (€0.8m) collectively are up 7% overall compared with first-half 2014. Individually, services & accessories revenue fll by 10% from €2.3m to €2.1m, while cells & sources doubled from €0.4m to €0.8m. Sales also reflect the first contribution by MBE Control Solutions of Santa Barbara, CA, USA (acquired in March), which provides MBE system maintenance and refurbishment services. Orders have fallen by 15% from €8m in first-half 2014 to €6.3m in first-half 2015. Specifically, MBE Systems orders have fallen by 19%, from €5.5m to €4.5m (comprising four MBE systems, including one production machine for Asia). Orders for services & accessories have fallen by 48% from €2.1m to €1.1m (which includes €0.3m from MBE Control Solutions). However, orders for cells & sources have risen by 83% from €0.4m to €0.7m (including prototype equipment for the OLED market). Regarding OLED flat-screen markets, in line with its development plan, Riber has delivered part of the linear cells to equip a pilot line in Korea and has launched initial on-site qualification tests. Despite orders falling from first-quarter 2015 (€4.5m), Riber says that a recovery in its order book from Q2's low is supported by a new research MBE system sold in July to an academic customer in France. Also, faced with a sluggish industrial market, during second-quarter 2015 Riber further strengthened its sales & marketing operations for the research market. "Order levels are building back up again, and we are rolling out major sales and marketing efforts

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to accelerate this momentum, which is reflected in a growing pipeline of potential orders," says Frédérick Goutard, chairman of the executive board. "Alongside this, in the OLED sector, we are continuing to develop our new range of cells, working closely with Korea's leading industrial firms in this business," he adds. "The full benefits of these promising developments are expected to be seen from 2016". Riber notes that, in the context of order levels improving but belatedly, deliveries will extend into 2016, suggesting a fiscal 2015 in line with last year. Detailed first-half earnings and the outlook for full-year 2015 will be issued on 25 September. Read more Veeco ships 50th EPIK 700 GaN MOCVD reactor in less than a year Semiconductor Today

Epitaxial deposition and process equipment maker Veeco Instruments Inc of Plainview, NY, USA has shipped the 50th TurboDisc EPIK 700 gallium nitride (GaN) metal-organic chemical vapor deposition (MOCVD) reactor since the system's introduction ten months ago. Since its launch in September 2014, the EPIK 700 MOCVD system has now been installed, qualified and accepted at multiple LED manufacturers in several key regions around the world. According to recent customer feedback, the TurboDisc EPIK 700 MOCVD system has delivered increased LED wafer production with best-in-class uniformity and easy process transfer between systems, saving both time and money, says Veeco. "Veeco's EPIK 700 system was designed to facilitate the acceleration of general lighting by combining the LED industry's lowest cost of ownership with its most technologically advanced reactor," says chairman & CEO John Peeler. "These innovations have allowed EPIK 700 customers to better satisfy the demand for solid-state lighting in existing and emerging applications, particularly in the area of general lighting," he adds. The EPIK 700 is Veeco's latest system in a line of MOCVD reactors. Since the introduction of the TurboDisc K465i GaN MOCVD system in 2010, Veeco has steadily increased its market share, becoming the global leader in MOCVD thin-film process equipment, it is reckoned. In 2011, Veeco

introduced what was said to be the industry's first multi-reactor MOCVD system, the TurboDisc MaxBright GaN multi-reactor MOCVD system. "The EPIK 700 system features the advanced TurboDisc reactor design with more than twice the capacity of Veeco's K465i reactor, which translates to higher throughput efficiency to conserve expensive fab floor space," says Jim Jenson, senior VP & general manager, Veeco MOCVD. "Fifty EPIK 700 reactors are the equivalent to more than 100 Veeco K465i MOCVD reactors," he notes. "This increased capacity, improved wafer uniformity and reduced operating expenses enable LED customers to achieve a cost per wafer savings of 20-40% over previous MOCVD systems." Read more Veeco enters profit, as EPIK system revenue recognition aids 33% growth in Q2 Semiconductor Today

For second-quarter 2015, epitaxial deposition and process equipment maker Veeco Instruments Inc of Plainview, NY, USA has reported revenue of $131.4m (the highest quarterly revenue since 2012), up 33.7% on $98.3m last quarter and up 38% on $95.1m a year ago. This includes results from Solid State Equipment Holdings LLC (SSEC) of Horsham, PA, USA (now Veeco Precision Surface Processing, i.e. PSP) since its acquisition on 4 December. The Advanced Packaging, MEMS & RF segment (mainly PSP) contributed 11% of total revenue (relatively level on last quarter). "We are cross-selling into our other market segment, and overall PSP sales were up nearly 28%," notes chief financial officer Sam Maheshwari. "Our Precision Surface Processing business is performing exceptionally well and demand for these products remains healthy," adds chairman & CEO John R. Peeler. "Our differentiated and highly flexible process technology is well established in the broader MEMS market and gaining momentum in the Advanced Packaging space." The Scientific & Industrial segment comprised 14% of total revenue (level with Q1). Data Storage segment revenue has bounced back, more than doubling sequentially (rising from 7% of total revenue to 13%).

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The Lighting, Display & Power Electronics segment (primarily MOCVD) contributed 62% of total revenue. In particular, Veeco recognized revenue on its first Propel gallium nitride (GaN) power electronics metal-organic chemical vapor deposition (MOCVD) system just six months after its launch last November. "Our top-line growth has been fueled by the rapid adoption of our TurboDisc EPIK700 MOCVD system [for GaN LED production, launched last September]," says chairman & CEO John R. Peeler. "We have now successfully demonstrated the tool's capabilities across multiple customers, which enabled us to begin recognizing revenue upon shipment towards the end of the second quarter," he adds. "Revenue levels were highly dependent on the timing of the transition of the EPIK product to our standard revenue-upon-shipment model," notes Maheshwari. "We achieved this significant milestone in late May, which was in line with our expectation," he adds. "As a result [in transitioning the new system to a bifurcated revenue model], EPIK tools which shipped after the transition date were included in Q2 revenue; EPIK tools that shipped prior to this transition date will remain in deferred revenue [totalling $55m at the end of Q2] until we receive final customer acceptance."

On a geographic basis, China rose from 45% of total revenue in Q1 to 50%, driven primarily by MOCVD sales to leading LED makers. The remaining 50% of revenue was spread fairly evenly across the USA, EMEA (Europe, the Middle

East & Africa) and Rest of the World (including Taiwan, Japan and Korea). Read more Aixtron's first-half revenue and margin suppressed by delayed customer qualifications for AIX R6 MOCVD tool Semiconductor Today

For first-half 2015, deposition equipment maker Aixtron SE of Herzogenrath, near Aachen, Germany has reported revenue of €80.7m (down 10% year-on-year on €90.1m in first-half 2014). Of total revenue, 79% came from Asia, 11% from Europe, and 10% from the USA. Equipment revenue was €57.9m (72% of total revenue, with the remaining 28% coming from spare parts & services). Of equipment revenue, by end application, LEDs comprised just 24% (down from 75% in first-half 2014), silicon 32% (up from just 8%), power electronics 19% (up from 5%), and optoelectronics 14% (up from 7%). In particular, second-quarter 2015 revenue was €40.4m, down by 13% on €46.2m a year ago but roughly levelling off after first-quarter 2015's €40.3m.

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Demand for LED chips is growing due to an increasing penetration of LED technology in the lighting market and the demand of LEDs for displays, with high utilization rates at many LED producers. But despite that, orders and shipments in first-half 2015 remained slow. "The weak revenue numbers are a clear reflection of not only the cautious investment behavior of our customers, but also of the AIX R6 qualification process, which has caused potential buyers to wait and see how the product performs other than buying the whole generation of equipment," says president & CEO Martin Goetzeler. "The AIX R6 Showerhead tool, our latest generation of MOCVD equipment [launched last November for the mass production of LEDs based on gallium nitride (GaN)], is not only important to our overall financial performance in this year but also to the long-term positioning of Aixtron within the LED market," notes chief operating officer Dr Bernd Schulte. "We have had the AIX R6 production qualified at one LED manufacturer. Including this customer, we have secured orders from now eight different customers, up from seven in the previous quarter. We are also getting additional inbound enquiries and interests from customers," he adds. "However, we should not hide the fact, together with our major customers, that it has taken longer than we would have liked to get the AIX R6 to the production stage. Based on detailed programs regarding hardware and process, we are closely collaborating with our customers to support their qualification targets." Read more Rubicon's revenue falls 20% in Q2, as 2-inch sapphire core sales and pricing hit by weak mobile market Semiconductor Today

For second-quarter 2015, Rubicon Technology Inc of Bensenville, IL, USA (which makes monocrystalline sapphire substrates and products for the LED, semiconductor and optical industries) has reported revenue of $7.1m, down 51% on $14.5m a year ago and down 20% on $8.9m last quarter due to weaker sapphire demand (most likely resulting from increased TV inventory levels and some seasonality in the LED light bulb market) and lower pricing.

"While sapphire pricing rose in the first half of last year, pricing has declined over the past several quarters and the current pricing environment is particularly tough," says president & CEO Bill Weissman. "The continued oversupply in the market along with weak currencies in Russia and Japan have been compounded by the current softness in the market." Specifically, demand from the mobile market was weaker, resulting particularly in lower 2-inch core volumes and additional pressure on pricing (which is down 18% on last quarter and almost halved from a year ago). Revenue from 2-inch cores has hence fallen further, from $6.4m a year ago and $4m last quarter to just $2.6m. Revenue from 4-inch cores rose from $1m to $1.2m, although that is still down on $3.2m a year ago. Revenue from 6-inch cores rose from just $23,000 last quarter to $171,000. Total revenue for cores fell further, from $9.6m a year ago and $5.1m last quarter to $4m. Overall wafer revenue was roughly unchanged sequentially. However, polished wafer sales have fallen further, from $2.6m a year ago and $1.43m last quarter to $0.84m because the firm's focus on wafer sales has shifted exclusively to patterned wafers, where it believe there is greater margin opportunity. Patterned sapphire substrate (PSS) wafer sales have hence begun to accelerate, from $0.26m a year ago then nearly doubling from $0.46m last quarter to $0.9m. Optical revenue fell by $578,000 from $1.77m last quarter to $1.19m due to lower sales volume. Read more

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PATENT APPLICATION

More than 200 new patent applications were published between 2015-07-02 and 2015-09-01.

Patent Applicants Number of

new patent applications

ILJIN LED 10

Toyoda Gosei 7

LG Electronics 6

LG Innotek 5

Panasonic 5 Other patent applicants: Asahi Chemical Industry, Avogy, Beijing University of Technology, Changzhou Institute of Technology, Chonbuk National University, CNRS - Centre National Recherche Scientifique, Dow Corning, Electronics & Telecommunications Research Institute, Enraytek Optoelectronics, Furukawa Electric, Globalwafers Japan, Gwangju Institute of Science &Technology, Hangzhou Silan Azure, HC Semitek, Hefei IRICO Epilight Technology, Hitachi Metals, HRL Laboratories, Huazhong University of Science & Technology, Industry Academic Cooperation Foundation, Infineon Technologies, Intel, Japan Wafer Global, Korea Electronics Telecomm, Marubun, Mitsubishi Chemical, Nagoya University, Nanjing University of Science & Technology, Nantong Tongfang Semiconductor, National Central University, National Institute of Standards & Technology, National R&D Riken, NGK Insulators, Nichia, Nippon Telegraph & Telephone (NTT), No 55 Institute of China Electronics Science & Technology, Nuflare Technology, Osram Opto Semiconductors, Phoenix Interface Technologies, Postech Foundation, Qorvo, Renesas Electronics, Ricoh, Saiokusu, Samsung Electronics, Sandia, Sanken Electric, Sciocs, Seoul Semiconductor, Seoul Viosys, Shanghai Institute of Microsystem & Information Technology, Sharp, Sino Nitride Semiconductor, Sixpoint Materials, Soraa, Soraa Laser Diode, South China Normal University, Stmicroelectronics, Sumitomo Electric Industries, Sun Yat Sen University, Sunedison Semiconductor, TSMC, Tokyo Electron, Tokyo Ohka Kogyo, Tokyo University of Science Educational Foundation, Toshiba, Toyota Central R&D Labs, Toyota Motor, Transform Japan, Translucent, Tsinghua Tongfang, Tsinghua University, Ulvac, Unist Academy Industry Research, Universite Francois Rabelais Tours, University of California, Ushio Electric, Xiangneng Hualei Optoelectronic Corppration, Xin Jiang University, Zhejiang Normal University, 13th Research Institute of China Electronics Technology …

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New patent applications selected by Knowmade Method and system for a gallium nitride vertical transistor Publ. Nb: US2015243758 Patent Applicant: Avogy (US)

A vertical JFET includes a GaN substrate comprising a drain of the JFET and a plurality of patterned epitaxial layers coupled to the GaN substrate. A distal epitaxial layer comprises a first part of a source channel and adjacent patterned epitaxial layers are separated by a gap having a predetermined distance. The vertical JFET also includes a plurality of regrown epitaxial layers coupled to the distal epitaxial layer and disposed in at least a portion of the gap. A proximal regrown epitaxial layer comprises a second part of the source channel. The vertical JFET further includes a source contact passing through portions of a distal regrown epitaxial layer and in electrical contact with the source channel, a gate contact in electrical contact with a distal regrown epitaxial layer, and a drain contact in electrical contact with the GaN substrate. Read more Vertical gallium nitride schottky diode Publ. Nb: US2015221782, CN104821341, FR3017242 Patent Applicant: STMicroelectronics (FR), CNRS-Centre National de la Recherche Scientifique (FR), Université François Rabelais (FR)

A Schottky diode may include a semiconductor substrate having first and second opposing surfaces, and a buffer layer over the first surface of the semiconductor substrate. The Schottky diode may include a first doped GaN layer over the buffer layer and having first and second opposing surfaces, the second surface of the first doped GaN layer being adjacent the buffer layer, and a second doped GaN layer over the second surface of the first doped GaN layer and having a dopant concentration level less than a dopant concentration level of the first doped GaN layer. The buffer layer, the first doped GaN layer, and the second doped GaN layer may define an opening. The Schottky diode may include a first metallization layer being coupled to the semiconductor substrate and to the first surface of the first doped GaN layer and being in the opening. Read more Method and structure for encapsulation and interconnection of transistors Publ. Nb: US9093394 Patent Applicant: HRL Laboratories (US)

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A semiconductor device comprises one or more transistors and two or more layers of dielectric material encapsulating a front side of said one or more transistors. The gate of each of said one or more transistors is located within a cavity, or air-box, in at least one of the dielectric layers, so that the gate terminal is physically separated from said dielectric material. Such an arrangement may reduce parasitic capacitance. In another arrangement, a semiconductor device comprises one or more gallium nitride high electron mobility transistors and one or more dielectric layers encapsulating a front side of said one or more transistors, wherein the gate terminal of each of said one or more transistors is located within a cavity in at least one of the one or more dielectric layers, separated from said dielectric material. Read more Side emitting type nitride semiconductor light-emitting device Publ. Nb: US2015188011, KR20150078295, WO2015102224 Patent Applicant: ILJIN LED (KR)

Disclosed is a side emitting type nitride semiconductor light-emitting device capable of omitting a lead frame mold cup and a lens and expanding the beam angle by emitting light in a side emitting manner. Read more

III-nitride based esd protection device Publ. Nb: US2015236008, DE102015101935, CN104851880 Patent Applicant: Infineon Technologies (DE)

An ESD (electrostatic discharge) protection device includes a first III-nitride p-i-n diode and a second III-nitride p-i-n diode connected to the first III-nitride p-i-n diode in an antiparallel arrangement configured to provide voltage clamping at 5V or less under forward bias of either the first or second III-nitride p-i-n diode for transient current in both forward and reverse directions. A corresponding method of manufacturing the ESD protection device is also provided. Read more Wide band gap transistors on non-native semiconductor substrates and methods of manufacture thereof Publ. Nb: WO2015099688 Patent Applicant: Intel (US)

Techniques are disclosed for forming a GaN transistor on a semiconductor substrate. An insulating layer forms on top of a semiconductor substrate. A trench, filled with a trench material comprising a III-V semiconductor material, forms through the insulating layer and extends into the semiconductor substrate. A channel structure,

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containing III-V material having a defect density lower than the trench material, forms directly on top of the insulating layer and adjacent to the trench. A source and drain form on opposite sides of the channel structure, and a gate forms on the channel structure. The semiconductor substrate forms a plane upon which both GaN transistors and other transistors can form. Read more Nitride semiconductor device and fabricating method thereof Publ. Nb: US2015200257, EP2897173, KR20150085724, JP2015135946 Patent Applicant: LG Electronics (KR)

A nitride semiconductor power device includes an AlGaN multilayer (120), which has changeable Al composition along a depositing direction, and Si x N y layer (150), so as to minimize an increase in a leakage current and a decrease in a breakdown voltage, which are caused while fabricating a heterojunction type HFET device. A semiconductor device (100) includes a buffer layer (110), an AlGaN multilayer (120) formed on the buffer layer (110), a GaN channel layer (130) formed on the AlGaN multilayer (120), and an AlGaN barrier layer (140) formed on the AlGaN multilayer (120), wherein aluminum (Al) composition of the AlGaN multilayer (120) changes along a direction that the AlGaN multilayer (120) is deposited. Read more

It is deep ultraviolet led and its production method Publ. Nb: JP5757512 Patent Applicant: Marubun Corporation; Toshiba Machine Co Ltd; National Research and Development RIKEN; ULVAC Inc; Tokyo Ohka Kogyo Co Ltd

Deeply being ultraviolet LED design wave length is designated as I**, the transparency, to the baseplate from opposite side it possesses p type AlGaN layer, in this order vis-a-vis reflector layer, and metal layer and p type GaN contact layer and wave length I** at least penetrates with the aforementioned p type GaN contact layer and the aforementioned p type AlGaN layer and it possesses the photo nick crystal periodic structure which becomes, at the same time, aforementioned photo nick crystal periodic structure is deep ultraviolet LED it features that it possesses the photo nick band gap. Read more

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Method for manufacturing rod-type light emitting device and rod-type light emitting device Publ. Nb: US2015214429, JP2015142020, KR20150090847 Patent Applicant: Tokyo Electron Limited (JP), The University of Nagoya University (JP)

There is provided a method for manufacturing a rod-type light emitting device, which includes: forming a rod having lateral surfaces and an upper surface on a GaN layer of a first conductivity-type, the rod being made of a GaN of the first conductivity-type; selectively growing a high-resistivity layer on the upper surface of the rod; forming a multi-quantum well layer to cover the lateral surfaces and the upper surface of the rod and the high-resistivity layer; and forming a GaN layer of a second conductivity-type to cover the multi-quantum well layer. Read more

Production method of nitride semiconductor device Publ. Nb: JP2015130374 Patent Applicant: Nippon Telegraph and Telephone - NTT (JP)

PROBLEM TO BE SOLVED: In the GaN vertical type transistor, while controlling the influence

which makes the current value at the time of transistor action decrease, miniaturizing element size try to be able operate by heavy-current. SOLUTION: The open part 103 which arrives in baseplate 101 on the baseplate 101 which has been exposed in the open part 103 of formation and insulating layer 102, 1st nitride semiconductor layer 104 of 1st electric conduction type, 2nd nitride semiconductor layer to grow 3rd nitride semiconductor layer 106 of 105 of 2nd electric conduction type, and 1st electric conduction type, to these orders selectively in insulating layer, 102 1st nitride semiconductor layer 104, 2nd nitride semiconductor layer 105, to form the prismatic section 121 which consists of the lamination structure of 3rd nitride semiconductor layer 106, after this, prismatic section 121The insulating layer 107 which covers the side is formed. Read more Method for producing a semiconductor layer sequence and optoelectronic semiconductor component Publ. Nb: DE102014102461, WO2015/128319 Patent Applicant: OSRAM Opto Semiconductors (DE)

The invention relates to a method for producing a semiconductor layer sequence, which method comprises the following steps: providing a growth substrate (50) having a growth surface (51) on a growth side (50a), growing a first nitridic semiconductor layer (10) on the growth side, growing a second nitridic semiconductor layer (20) on the first nitridic semiconductor layer (10), wherein the second nitridic semiconductor layer (20) has at least one opening (21) or at least one opening (21) is

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produced in the second nitridic semiconductor layer (20) or at least one opening (21) in the second nitridic semiconductor layer (20) arises during the growth, removing at least part of the first nitridic semiconductor layer (10) through the openings (21) in the second nitridic semiconductor layer (20), growing a third nitridic semiconductor layer (30) on the second nitridic semiconductor layer (20), wherein the third nitridic semiconductor layer (30) covers the openings (21) at least in some locations. Read more Nitride semiconductor device Publ. Nb: WO2015122135 Patent Applicant: Panasonic (JP)

Disclosed is a nitride semiconductor device that is provided with: a substrate (1); a first nitride semiconductor layer (2), which is formed on the substrate (1), and which has a C-plane as a main surface; a second nitride semiconductor layer (3), which is formed on the first nitride semiconductor layer (2), and which has a p-type conductivity; and a first opening (8), which is formed in the second nitride semiconductor layer (3), and which reaches as far as the first nitride semiconductor layer (2). The nitride semiconductor device is also provided with: a third nitride semiconductor layer (6) that is formed so as to cover the first opening (8) in the second nitride semiconductor layer (3); a first electrode (10) that is formed on the third nitride semiconductor layer (6) so as to include a region of the first opening (8); and a second electrode (12) that is formed on the rear surface of the substrate (1). A layer thickness (Gx) of the third

nitride semiconductor layer (6) on a side wall of the first opening (8), said layer thickness being in the direction parallel to the C-plane, is more than a layer thickness (Gy) of the third nitride semiconductor layer (6) on a flat section outside of the first opening (8), said layer thickness being in the direction perpendicular to the C-plane. Read more Method for fabricating triangular prismatic m-plane nitride semiconductor light-emitting diode Publ. Nb: US2015200330, JP2015149470 Patent Applicant: Panasonic (JP)

When a belt-like nitride semiconductor stacking structure 110 having a principal plane of an m-plane is broken along a linear groove 104, two or more side surfaces may be formed on the lateral side thereof. This decreases the fabrication efficiency of the triangular prismatic m-plane nitride semiconductor light-emitting diode. To solve this problem, Angle X of not less than 75 degrees and not more than 105 degrees is formed between the linear groove 104 and one cleavage axis selected from the group consisting of an a-axis and a c-axis. Then, the belt-like nitride semiconductor stacking structure 110 was broken along the linear groove 104 to form a quadratic prismatic nitride semiconductor stacking structure 120. Subsequently, the quadratic prismatic nitride semiconductor stacking structure 120 is broken along another linear groove 106 to obtain a triangular prismatic m-plane nitride semiconductor light-emitting diode 130. Read more

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Doped gallium nitride high-electron mobility transistor Publ. Nb: US2015200287, DE102015000190, JP2015135965, TW201532279 Patent Applicant: Qorvo (US)

Embodiments include high electron mobility transistors (HEMTs) comprising a substrate and a barrier layer including a doped component. The doped component may be a germanium doped layer or a germanium doped pulse. Other embodiments may include methods for fabricating such a HEMT. Read more Mechanical compression-based method for the reduction of defects in semiconductors Publ. Nb: US2015206765 Patent Applicant: Sandia Corporation (US)

A high pressure-directed engineering method enables reduced defect semiconductor materials that are unattainable by other chemical and physical methods. Experimental results show that hydraulic pressures as low as 0.5 GPa can eliminate stacking faults and

significantly reduce point defects, leading to improved materials quality in semiconductors, such as GaN. Read more Method for manufacturing gallium and nitrogen bearing laser devices with improved usage of substrate material Publ. Nb: CN104836117, US2015229107, US2015229100, DE102014223196, JP2015154074 Patent Applicant: Soraa Laser Diode (US)

A method for manufacturing a laser diode device includes providing a substrate having a surface region and forming epitaxial material overlying the surface region, the epitaxial material comprising an n-type cladding region, an active region comprising at least one active layer overlying the n-type cladding region, and a p-type cladding region overlying the active layer region. The epitaxial material is patterned to form a plurality of dice, each of the dice corresponding to at least one laser device, characterized by a first pitch between a pair of dice, the first pitch being less than a design width. Each of the plurality of dice are transferred to a carrier wafer such that each pair of dice is configured with a second pitch between each pair of dice, the second pitch being larger than the first pitch. Read more

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Semiconductor device and its production method Publ. Nb: JP2015133407 Patent Applicant: Transform Japan (JP)

PROBLEM TO BE SOLVED: While decreasing contact resistance, it improves resisting pressure. SOLUTION: The semiconductor device, electronic travelling layer the nitride semiconductor lamination structure the drain electrode 7 which is provided on 4 5 which includes 3 and electronic supply layer 4 and electronic supply layer and source electrode it has with the gate electrode 6 where, is provided in the upper part of 8 and nitride semiconductor lamination structure 5 drain electrode 7, it possesses plural concave sections 7X and the plural convex sections 7Y which, extend parallel to the cross direction of the gate electrode in the contact section 7A which touches to electronic supply layer 4 most gate electrode 6 side that try it becomes the concave section. Read more

Engineered substrates for use in crystalline-nitride based devices Publ. Nb: US2015187888, WO2015103274, TW201530757 Patent Applicant: Veeco Instruments (US)

A spalling process can be employed to generate a fracture at a predetermined depth within a high quality crystalline nitride substrate, such as a bulk GaN substrate. A first crystalline conductive film layer can be separated, along the line of fracture, from the crystalline nitride substrate and subsequently bonded to a layered stack including a traditional lower-cost substrate. If the spalled surface of the first crystalline conductive film layer is exposed in the resulting structure, the structure can act as a substrate on which high quality GaN-based devices can be grown. Read more

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