nonpolar and semipolar iii-nitride optoelectronic materials and

1

Nonpolar and Semipolar III-Nitride Optoelectronic Materials and Devices

Prof. Daniel Feezell Center for High Technology Materials

Department of Electrical and Computer Engineering

University of New Mexico, Albuquerque, NM – 87131

[email protected]

505-272-7823

D. Feezell

mailto:[email protected]

2

Group: 3 postdocs, 8 graduate students, 1 undergraduate student, 1 MOCVD research engineer

III-Nitride Materials and Devices Group

D. Feezell

www.feezellgroup.com

MOCVD Nanofabrication

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Outline

• Introduction to III-nitride materials

• Characteristics and advantages of nonpolar/semipolar III-nitrides

• Semipolar (202 1 ) and nonpolar (101 0) InGaN/GaN LEDs

• Nonpolar/semipolar LEDs based on bottom-up selective-area epitaxy

• Polarization-pinned nonpolar vertical-cavity surface-emitting lasers

• Summary

D. Feezell

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Introduction to III-Nitrides

D. Feezell

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III-Nitride Materials

• Direct band gaps ranging from 0.7 eV (InN) to 3.4 eV (GaN) to 6.0 eV (AlN)

• Enable high-performance UV, violet, blue, and green emitters

• Robust against high dislocation densities (108 cm-2), thermally stable, radiation tolerant

• In general, alloys not lattice matched to GaN

D. Feezell

• Solid-state lighting

• Visible and UV lasers

• Power electronics

• Multijunction solar cells

• Radiation hard devices

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• Two interlaced hexagonal close

packed (HCP) lattices

• Horizontal planes of Ga atoms and

N atoms

• Each unit cell contains 2 Ga atoms

and 2 N atoms

• Bonding in GaN is 60% covalent

with 40% ionic character

GaN Crystal Structure (Wurtzite)

D. Feezell

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Select GaN Crystal Planes

D. Feezell

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Polarization in III-Nitrides

• Piezoelectric polarization (PPZ) – due to strain (e.g. – InGaN/GaN or AlGaN/GaN)

• Spontaneous polarization (PSP) – present in unstrained lattices and is due to charge asymmetry

• PPE becomes larger for higher indium contents (i.e. – green and yellow emitters)

Polarizations induce large internal electric fields (~MV/cm) which distort the band diagrams

We can use nonpolar and semipolar orientations to eliminate the effects of polarization

D. Feezell

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Characteristics and Advantages of Nonpolar/Semipolar III-Nitrides

D. Feezell

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Energy Band Diagrams for SQW Blue LEDs

𝐒𝐞𝐦𝐢𝐩𝐨𝐥𝐚𝐫 (𝟐𝟎𝟐 𝟏)

𝐒𝐞𝐦𝐢𝐩𝐨𝐥𝐚𝐫 (𝟐𝟎𝟐 𝟏 )

𝐏𝐨𝐥𝐚𝐫 (𝟎𝟎𝟎𝟏)

𝐍𝐨𝐧𝐩𝐨𝐥𝐚𝐫 (𝟏𝟎𝟏 𝟎) D. Feezell, J. Disp. Technol. 9, 190-198 (2013)

D. Feezell

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Wavefunction Overlaps for SQW Blue LEDs

3 nm In0.23Ga0.77N SQW LEDs ( 450 nm)

simulated using SiLENSe

Wavefunction overlap is strongly affected by direction and magnitude of internal electric fields

D. Feezell

D. Feezell, J. Disp. Technol. 9, 190-198 (2013)

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m-plane:

• High output power for QW widths up to 20 nm

• Pmax for QW widths of 8-12 nm

Violet LEDs: 6x MQW QW-width series

Novel Device Designs

c-plane:

• QWs 3 nm thick

• Polarization-related fields

• Decline in output power for thick QWs

K. C. Kim et al., Appl. Phys. Lett. 91, 181120 (2007).

Reduction of internal electric fields enables novel devices designs

D. Feezell

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Polarized Emission

Band structures after Scheibenzuber, Phys. Rev. B 80, 115320 (2009).

c-p

lan

e (

po

lar)

m

-pla

ne (

no

np

ola

r)

𝒀′ → 𝑬 ⊥ 𝒄

𝑿′ → 𝑬 ∥ 𝒄

𝑯𝑯 , 𝑳𝑯 = 𝑿 ± 𝒊𝒀 → 𝒖𝒏𝒑𝒐𝒍𝒂𝒓𝒊𝒛𝒆𝒅 𝒆𝒎𝒊𝒔𝒔𝒊𝒐𝒏

H. Tsujimura et al., Jpn. J. Appl. Phys. 42, L1010 (2007).

Nonpolar VCSELs are polarization pinned with E c

D. Feezell

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• QCSE reduced

• Optical matrix elements increased

• Emission anisotropic

• Optical gain increased

• Hole effective mass reduced

• Transparency carrier density reduced

• Growth and design flexibility improved

Summary of Benefits for Nonpolar/Semipolar

D. Feezell

D. Feezell and S. Nakamura, “Nonpolar and Semipolar Group III-Nitride Lasers,” in Semiconductor Lasers: Fundamentals and Applications, Edited by A. Baranov and E Tournie, Woodhead Publishing, ISBN13: 9780857091215 (2013).

15

Semipolar 202 1 and Nonpolar 101 0 InGaN/GaN LEDs

D. Feezell

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Applications for III-Nitride LEDs

Solid-state lighting

Backlighting

Architectural lighting Automotive lighting

Horticulture Street lighting

D. Feezell

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White LEDs vs. Conventional Lighting

• Available >130 lm/W phosphor-converted commercial LED products

• Emerging >200 lm/W LED prototypes

• ~250 lm/W possible for phosphor converted LEDs M. Krames, CLEO (2009)

Nichia (small chip)

249 lm/W

Nichia (power chip)

183 lm/W

D. Feezell

Cree

276 lm/W

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Issues Plaguing GaN-Based LEDs

Green Gap Efficiency Droop

• Auger recombination

• Carrier leakage

• Polarization-related electric fields

• Strain

• Threading dislocations

• Indium inhomogeneity

D. Feezell

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Semipolar (202 1 ) is a promising new orientation:

• Low polarization-related electric fields

• Fields in same direction as c-plane, ¼ the magnitude

• Large wavefunction overlap for LED current densities

• Very small blue shift

• Very narrow FWHM

• Highly polarized emission

• High indium uptake for high growth temperature

Semipolar 202 1 Light-Emitting Diodes

D. Feezell

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Growth on Free-Standing GaN Substrates

• Mitsubishi Chemical Corporation

• Dislocation density < 5x106 cm-2

• MOCVD growth conditions are similar to those for c-plane on sapphire

Nonpolar/semipolar GaN substrates cut from HVPE-grown c-plane GaN boules

MQW LED

K. Fujito et al., MRS Bulletin 34 313 (2009)

D. Feezell

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*TEM image courtesy of Feng Wu

Higher growth temperature results in high-quality InGaN active regions

High Quality Blue InGaN (202 1 ) QWs

D. Feezell

C. Pan et al., Appl. Phys. Express 5 062103 (2012)

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Transparent Package

LED Structure and Process

• Top-emitting ITO-based chip

• 0.1 mm2 active area

• Patterned backside roughening

• ZnO-based transparent LED package

Y. Zhao et. al., Appl. Phys. Express 3 10210 (2010) C. Pan et. al., Jpn. J. Appl. Phys. 49 080210 (2010)

ZnO Stand

ITO-based p-contact

202 1 GaN

n-GaN

n-InGaN/GaN SL

InGaN/GaN QWs

AlGaN EBL

p-GaN

ITO Ti/Au

Ti/Au

Ti/Al/Ni/Au

Simulated Light Extraction Efficiency ~75%

D. Feezell

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Blue (202 1 ) LEDs: EQE vs. Current Density


• Thick (12 nm) SQW active region

• ITO-based chip

𝐷𝑟𝑜𝑜𝑝 % =(𝐸𝑄𝐸𝑃𝑒𝑎𝑘−𝐸𝑄𝐸)

𝐸𝑄𝐸𝑃𝑒𝑎𝑘

35 (A/cm2) 100 (A/cm2) 200 (A/cm2) 300 (A/cm2) 400 (A/cm2)

EQE (%) 52.4 50.1 45.3 43.0 41.2

Droop (%) 0.7 5.1 14.1 18.4 21.9


D. Feezell

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Blue (202 1 ) LEDs: LOP vs. Current Density


• Thick (12 nm) SQW active region

• >450 mW peak output power

• ~5 chips needed for 60 W incandescent replacement

35 (A/cm2) 100 (A/cm2) 200 (A/cm2) 300 (A/cm2) 400 (A/cm2)

LOP (mW) 51.2 140.0 253.4 360.9 460.3

D. Feezell


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• Studied IQE and carrier lifetimes in three 202 1 structures

• 12 nm total active region thickness (1x12 nm, 2x6 nm, 3x4 nm)

• 450 nm peak wavelength

Blue (202 1 ) LEDs: IQE and Carrier Lifetimes

Epitaxial Structures

Wafer 1 QW 2 QW 3 QW

141127EL 141127FL 141127DL

p/p++ GaN 110 nm (Mg = 2e19 cm-3/1.6e20 cm-3)

AlGaN EBL 10 nm (Mg = 1e19 cm-3)

GaN Barrier 12 nm (uid)

Active region 12 nm InGaN QW

6 nm InGaN QW 4 nm InGaN QW

4 nm GaN barrier

4 nm GaN barrier

4 nm InGaN QW

4 nm GaN barrier

6 nm InGaN QW 4 nm InGaN QW

GaN Barrier 12 nm (uid)

n GaN 2 μm (Si = 3e18 cm-3)

D. Feezell

S. Okur, et al., submitted to Optics Express

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Temperature-dependent and time-resolved photoluminescence

Micro-Photoluminescence (µ-PL) System

D. Feezell

~50 µm spot diameter

Collaboration with Center for Integrated

Nanotechnologies

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• Non-radiative lifetime assumed to be infinite at 10 K

• IQE maximum in the 1 x 12 nm structure

• Excitation power level accesses SRH and radiative regimes

Internal Quantum Efficiency (IQE)

D. Feezell

𝐼𝑄𝐸 = 𝐼295𝐾 𝜆 𝑑𝜆

𝐼10𝐾 𝜆 𝑑𝜆

1x1017

1x1018

102

103

104

105

106

107

LT

Inte

gra

ted

PL

In

t. (

arb

. u

nit)

Carrier Density (cm-3)

RT

X10

0 1x1018

2x1018

3x1018

0.0

0.2

0.4

0.6

0.8

1.0

400 420 440 460 480 500 520 540

0

1

2

3

4

1x12 nm

2x6 nm

3x4 nm

IQE


Active Region

PL I

nte

nsity (

arb

. unit)

Wavelength (nm)

1x12 nm

2x6 nm

3x4 nm


28

0 10 20 30 4010

-4

10-3

10-2

10-1

100

PL I

nte

nsity (

arb

. u

nit)

Delay Time (ns)

1x12 nm

2x6 nm

3x4 nm

• TRPL decay fit with bi-exponential function (𝐴1𝑒−𝑡 𝜏1 + 𝐴2𝑒−𝑡 𝜏2 ) to extract PL lifetime

• Slower decay associated with carrier lifetime

• PL lifetime longest for 1 x 12 nm structure

Time-Resolved Photoluminescence

D. Feezell

22.5 µJ/cm2 0 1x10

182x10

183x10

1810

-1

100

101

1x12 nm

2x6 nm

3x4 nm

PL

Lifetim

e (

ns)



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• Similar radiative lifetime for all structures

• Longer non-radiative lifetime for thicker QWs

• Correlated with higher IQE for thicker QWs

• Related to influence of QW interface defects

Radiative and Non-Radiative Carrier Lifetimes

.

D. Feezell

𝜏𝑅 = 𝜏𝑃𝐿 𝐼𝑄𝐸 , 1 𝜏𝑃𝐿 = 1 𝜏𝑅 + 1 𝜏𝑁𝑅

100

101

102

103

0 1x1018

2x1018

3x1018

10-1

100

101

102

103

1x12 nm

2x6 nm

3x4 nm

Ra

d (

ns)

No

nR

ad (

ns)



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The Second Wave: Smart Lighting

Translational Research Testbeds

Goal: Plenoptic light field sensing • Color quality • Intensity • Direction (Light Flow) • Data

Goal: Maximize light quality and minimize energy use

Goal: Communications with Illumination (Dual Use)

Goal: Luminaires with dynamic • Brightness control • Spectral control • Beam shaping capability • Integrated data communications

Slide courtesy of Prof. R. Karlicek, RPI

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• Short carrier lifetime on nonpolar

• Micro-LEDs for large RC bandwidth

• 3 x 6 nm QWs, 15 nm barriers

• RF bandwidth characterized

High-Speed Nonpolar 101 0 LEDs

0 1 2 3 4 5 6 7 8 9 100

2

4

6

8

10

12

300 400 500 600 700

453 nm

EL

In

ten

sit

y (

a. u

.)

Wavelength (nm)

Vo

ltag

e (

V)

Current density (kA/cm2)

Lig

ht

Po

we

r (a

. u

.)

0

200

400

600

800

1000

D. Feezell

A. Rashidi, et al., submitted to Photon. Technol. Lett.

32

• Maximum 3 dB bandwidth is 524 MHz at 10 kA/cm2

• Bandwidth increases with current density but saturates due to heating and carrier escape

• Among the highest bandwidths reported for GaN-based LEDs

RF Bandwidth Characterization

10 100 1000-18

-16

-14

-12

-10

-8

-6

-4

-2

0

2

No

rma

lize

d p

ow

er

(dB

)

Frequency (MHz)

1 kA/cm2

3 kA/cm2

5 kA/cm2

8 kA/cm2

10 kA/cm2

3-dB line

(a)

0 1 2 3 4 5 6 7 8 9 10 11

300

350

400

450

500

550

3-d

B b

an

dw

idth

(M

Hz)


(b)

D. Feezell

𝑓3𝑑𝐵 ≈ 1

2𝜋

1

(𝜏𝑠𝑝2 + 𝜏𝑅𝐶

2 )1/2

60 µm diameter


33

Equivalent Circuit Model

200 400 600 800 1000

15

20

25

30

35

40

45

Re

(Z)

(Oh

ms

)

Frequency (MHz)

Real (Z)

fit

Value Standard Error

R 29.49127 0.01882

C 1.39642E-11 2.37634E-14

Rs 11.44454 0.01912

200 400 600 800 1000-14

-12

-10

-8

-6

-4

-2

0

Im(Z

)(O

hm

s)

Frequency (MHz)

Imaginary (Z)

fit

Value Standard Error

R 29.49 0

C 1.39E-11 0

L 7.87816E-10 1.83447E-12

2

2 2 2 2s

( )(1 R C )(R j L)

R j R CH

R j R C

D. Feezell

Fitting real and imaginary parts of the transfer function yields R and C


34

• LEDs are currently carrier lifetime limited since 𝑓𝑅𝐶 > 𝑓3𝑑𝐵

• Reduce active region volume to increase carrier density (𝑅𝑠𝑝 ∝ 𝑁2)

• Reduce barrier widths to increase tunneling

RC Bandwidth

0 1 2 3 4 5 6 7 8 9 10 111.0

1.1

1.2

1.3

1.4

1.5

1.6

1.7

1.8

1.9

R

C b

an

dw

idth

(G

Hz)


D. Feezell

𝑓𝑅𝐶 = 1

2𝜋

1

𝜏𝑅𝐶

Frequency response of equivalent circuit plotted and RC limited 3 dB bandwidth determined


35

Bottom-Up Selective-Area Growth

D. Feezell

36

Core-Shell Nanostructure LEDs

Potential Advantages of Nanowall LEDs:

• Polarization-free, nonpolar (m-plane) active regions will help reduce droop

• Large effective active region area will reduce carrier density for a given current density and

mitigate droop

• Elimination of threading dislocations (TDs) will reduce non-radiative recombination and improve

lifetime

• Strain relaxed structures may allow for higher indium contents without defect generation

(potential green gap solution)

• Cost effective nonpolar/semipolar structures in patterned dielectric apertures on sapphire or

silicon

nonpolar

InGaN active

region

SiNx

Al2O3 or Si substrate

buffer/template

n-GaN p-G

aN

ITO

transparent

electrode

D. Feezell

37

• Threading dislocations bend 90°near free surface

Large areas of defect-free nanostructures

Dislocation free regions

Threading dislocations

A. Rishinaramangalam et al., EMC (2010)

Core-Shell Advantages

• Larger effective active region area for the same planar footprint Lower carrier density for a given current

38

Nanostructure Template Processing

Sapphire

n-GaN

SiNx

Sapphire

n-GaN

SiNx PR

Sapphire

n-GaN

SiNx PR

Sapphire

n-GaN

SiNx Ni

Sapphire

n-GaN

SiNx Ni

Sapphire

n-GaN

SiNx

1) Starting wafer 2) Spin ARC and PR 3) Interferometric lithography

4) Ni deposition and lift-off 5) Secondary photolithography

and RIE of SiNx

6) Liftoff and piranha clean

PR

D. Feezell

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• Nanoscale light-emitting diodes

• Nanoscale lasers

• Nanoscale transistors

• Solar cells

• Intersubband detectors

• Hydrogen generation

Core-Shell Nanostructures - Applications

3 µm

3 µm 3 µm

3 µm

D. Feezell

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Pulsed Mode MOCVD Technique

• Pulsed mode technique → locally

low V/III ratio

• Temperature from 900oC to 950oC

• Pressure 100 Torr

• TMGa flow 26.7 µmol/min

• V/III ratio of 100

• H2 flow of 3000 sccm

• N2 flow of 1000 sccm

Y. T. Lin et.al. Nanotechnology. 23 (46) (2012)

D. Feezell

A. Rishinaramangalam et al., J. Electron. Mat. 44, 1255 (2015)

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GaN Cores with 3X InGaN Quantum Wells

InGaN quantum wells on nanowires, nanowalls, and triangular stripes

D. Feezell

A. Rishinaramangalam et al., J. Electron. Mat. 44, 1255 (2015)

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Triangular Nanostripes

• Higher indium uptake on {101 1} family of planes

• Low polarization-related electric fields compared to c-plane

• High light extraction efficiency

• Continuous flow MOCVD

• Key challenge is current leakage in the diode

5 µm

10 µm

0.5 µm

n GaN

InGaN/GaN

QWs

D. Feezell

43

• Addition of n-AlGaN underlayer significantly reduces leakage current

• Addition of p-AlGaN electron blocking layer (EBL) has smaller effect

• Poly-AlGaN grows on dielectric mask, covering the mask and filling voids

• Effect on impurity concentration shown with SIMS

Leakage Current Reduction with AlGaN

D. Feezell

A. Rishinaramangalam, et al., submitted to Appl. Phys. Mat.

44

• Silicon and oxygen impurities significantly reduced in sample with AlGaN underlayer

• Mg incorporation increased in sample with AlGaN underlayer

• Leakage current eliminated by addition of AlGaN underlayer

SIMS Profiles Without and With Underlayer

D. Feezell

Without underlayer With underlayer

A. Rishinaramangalam, et al., submitted to Appl. Phys. Mat.

45

Electrically Injected Triangular Nanostripe LEDs

D. Feezell

A. Rishinaramangalam, et al., Appl. Phys. Express 9, 032101 (2016)

• Spectra exhibit multiple evolving peaks

• Initial blue shift evolves to stable wavelength at higher current

• Broad spectrum related to QW non-uniformities and poor current spreading

*Unpackaged, on-wafer measurement

46

• Single growth of arrays with different pitches

• Red shift as pitch increases

• Potential for monolithic multi-color LEDs

Electrically Injected Nanowire LEDs

-6 -4 -2 0 2 4 6

-3

0

3

6

9

12

Cu

rre

nt

De

ns

ity

(A

/cm

2)

Voltage (V)

D. Feezell

M. Nami, et al., submitted to Nanotechnology (2016)

47

• EL spectra show broad emission and evolving dominant wavelength

• PL spectra show broad emission but no change in shape

Room-Temperature PL and EL

PL: 405 nm excitation EL

D. Feezell

360 400 440 480 520 560 600 640 680

102

103

104

105

106

EL

Inte

nsity (

arb

. un

its)

Wavelength (nm)

3.40

6.80

10.2

13.6

17.0

20.4

23.8

27.2

30.6

34.0

51.0

68.0

Current

Density

(A/cm2)

400 440 480 520 560 600 640 680

100

101

102

103

104

105

PL Inte

nsity (

arb

. units)

Wavelength (nm)

0.04

0.18

0.35

1.75

3.50

8.75

17.5

26.3

35.0

43.8

52.5

63.0

Energy

Density

(J/cm2)

n-GaN

S. Okur et al., submitted to Appl. Phys. Letters

48

• Indium composition higher near the apex

• QWs thicker near the apex

• Poor current spreading leads to non-uniform injection, causing change in wavelength with current

• Longer wavelengths from the apex, shorter wavelengths from the sidewalls

TEM and EDS Show QW Non-Uniformities

D. Feezell

A. Rishinaramangalam, et al., Appl. Phys. Express 9, 032101 (2016)

3.3 V 6.5 V


49

• TEM, EDS, and current spreading simulations indicate longer wavelength emission from the apex and shorter wavelength emission from the sidewalls

• Spectrally resolved integrated PL gives an indication of the IQE in different regions of the stripe (e.g., apex vs. sidewalls)

• IQE is higher in the longer wavelength portion of the spectrum!

Spectrally Resolved Internal Quantum Efficiency


D. Feezell

0 20 40 600.0

0.2

0.4

0.6

0.8

1.0

Below 450 nm

Above 450 nm

IQE

Energy Density (J/cm2)

10-2

10-1

100

101

102

101

102

103

104

105

106

107

108

IQE = 100% line

Below 450 nm RT

Above 450 nm RT

Below 450 nm LT

Above 450 nm LT

Inte

gra

ted

PL

In

ten

sity (

arb

. u

nits)


IQE 100% line

𝐼𝑄𝐸 = 𝜂 ∗𝐼𝑃𝐿 (𝑅𝑇)

𝐼𝑃𝐿 (𝐿𝑇)

Y. Iwata et. al, J. Appl. Phys. 117, 075701 (2015).

50

0 200 400 600 800 1000 1200

420 nm

440 nm

PL

In

ten

sity (

arb

. u

nits)

460 nm

Delay Time (ps)

480 nm

D. Feezell


420 430 440 450 460 470 480100

120

140

160

180

200

220

240

0.04 J/cm2

0.35 J/cm2

3.50 J/cm2

35.0 J/cm2

PL L

ifetim

e (

ps)

Wavelength (nm)

PL Lifetimes

• PL transients measured within a 5 nm linewidth around central wavelengths of 420, 440, 460, 480 nm at different excitation levels

• PL lifetime (𝜏) generally increases as wavelength increases and as injection level increases

35 μJ/cm2

𝐴𝑒−𝑡 𝜏

51 D. Feezell


10-2

10-1

100

101

102

200

400

600

800

1000

420 nm nonrad. rec. lifetime

480 nm nonrad. rec. lifetime

420 nm rad. rec. lifetime

480 nm rad. rec. lifetime

Life

tim

e (

ps)


Radiative and Non-Radiative Carrier Lifetimes

• Radiative recombination lifetimes for the two central wavelengths are very similar in magnitude

• Non-radiative recombination lifetimes around 480 nm are at least two times larger than those around 420 nm lower density of defects near the apex, reduced strain near the apex, inhomogeneous indium composition near the apex

I. Tischer et. al, J. Mater. Res. 2, 7 (2015).

Weng et al., Nanoscale Research Letters (2015)

52

Nonpolar 101 0 GaN-Based VCSELs

D. Feezell

53

VCSEL Geometry and Characteristics

Invented by Kenichi Iga at the Tokyo Institute of Technology (1977)

S.O. Kasap, Optoelectronics and Photonics (2013)

D. Feezell

• Low power consumption

• Small device footprint

• Circular output beam

• Single-longitudinal-mode operation

• Densely-packed, two-dimensional arrays

• Wafer-level characterization

One challenge is achieving stable and predictable polarization of the output

54

Applications for GaN-Based VCSELs

Optical data storage

Head-up displays

High-resolution printing Projectors

Bio-sensing

D. Feezell

Chip-scale atomic clocks

55

Nonpolar GaN-Based VCSELs

Nonpolar GaN Flip-Chip Process

III-Nitrides VCSELs

Small footprint, low power consumption,

single-mode operation

Large optical gain and emission with polarization stability Overcomes key materials challenges

Nonpolar GaN enables polarization-pinned VCSELs

Access to UV wavelengths

D. Feezell

56

Polarization-Pinned Emission

Angle-resolved emission intensity nonpolar VCSEL

• Polarization of the light output pinned with E c

• Confirmed on multiple devices and multiple wavelengths under a range of injection levels

• Polarization ratio of ~100% measured

• Advantageous for polarization-sensitive optical systems: spectroscopy, atomic clocks, data storage, backlighting

C. Holder, et al., Appl. Phys. Lett. 105, 031111 (2014)

D. Feezell

57

• Nonpolar/semipolar III-nitrides eliminate effects from polarization-related electric fields

– High optical efficiency and gain

– Fast carrier lifetime

– Polarized emission

– Lower QCSE - design flexibility

• Demonstrated high-efficiency LEDs with low droop, high IQE, and large modulation bandwidth on free-standing GaN substrates

• Nanostructures exhibit unique properties that may be beneficial for solving some long-standing III-nitride materials issues

• Demonstrated electrically injected nanostructure LEDs and analyzed the QW properties in core-shell structures

• Higher efficiency green emitters may be enabled by growth on strain-relaxed 3D structures

• Nonpolar GaN enables polarization pinned UV and visible VCSELs

Summary

D. Feezell

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Funding Sources

D. Feezell

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Thank You!

D. Feezell

nonpolar and semipolar iii-nitride optoelectronic materials and

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