physical phenomena for terahertz electronic devices jérémi torres institute of electronics of the...
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Physical Phenomenafor TeraHertz
Electronic Devices
Jérémi TORRESInstitute of Electronics of the South
University MontpellierFrance
Outline
•TeraHertz : Generalities
•Physical phenomena
1. Plasma-waves
2. Optical-phonon resonance
3. Conclusions
The High-Frequency Investigation Group
MicrowavesAntennas/
RadarsEM
CompatibilityRFID
TheoryMonte Carlo
HydrodynamicDrift-Diffusion
ExperimentsPhotoexcitation
THz devicesNear-field
EM cartography
The TeraHertz “gap”
Low costCompact
Room temperature Continuous-wave
TunableIntegration
Electronics Photonics
f = 1012 Hz, 300 GHz - 10 THz, λ = 1 mm - 30 μm
Proc. of IEEE 23, 10 (2005)
Power vs frequency
Optical THz DevicesIndirect
• Laser Beating + photoconductor
• Femtosecond laser + nonlinear cristal
Difficulties: complexity, cost, magnetic field, maintenance,
temperature
Direct
• Gas laser
• Free electron laser
• p-Ge laser
• Quantum cascade laser
Electronic THz Devices
Indirect
• Multiplication
• Nonlinearities
Difficulties:
current, temperature, contact resistance, efficiency, noise
Direct• Gunn, RTD, Impatt diodes
• Schottky, varactor diodes
• Magnetron, Carcinotron
• FETs, HEMTs
Main Features of THz Radiation
•Non ionizing
•Strong interaction with molecules
•Transmitted through many materials
•Higher resolution than microwaves
Applications in SpectroscopyPhysics: THz Time Domain Spectroscopy,
dynamics of electrons, holes, phonons
Applications in Spectroscopy
Chemistry: chemical reactions, combustion, pollution, environment control
(Grischkowski, Oklahoma State Univ.)
Applications in SpectroscopyAstronomy: atmospheric window, detection of molecules, atoms, ionized gas
Progr. Quant. Electr. 28, 1 (2004)
Applications in TelecommunicationsTeraHertz antennas, wireless
communication
Applications in Imaging (T-Ray)
Inspection materials/devices/systems
Industry(Planken, Univ. Delft)
Applications in Imaging (T-Ray)
Medicine
Tooth decay(TeraView)
Applications in Imaging (T-Ray)
Medicine
Dermatology(Teraview)
Courtesy of Teraview
Applications in Imaging (T-Ray)Security
1. THz Nanotransistors
… exploiting plasma waves
Experiments on InGaAs HEMTs
Origin of the peaks?
Appl. Phys. Lett. 80, 3433 (2002)
THz oscillations from plasma-waves
3D plasma oscillations Analogy : harmonic oscillator
Practical applications : High Electron Mobility
Transistor
Tunable frequency with Vg
Travelling plasma waves
vdrift+vplasmavdrift-vplasma
Travelling plasma waves
Mascaret over the Dordogne riverhttp://www.archaero.com/mascaret.htm
Stationary plasma waves
n = 1 f = 0.9 THz n = 3 f = 2.7 THz
Plasma waves in HEMTs
Plasma synchronization by optical beating
Appl. Phys. Lett. 89, 201101 (2006)
THz beating
Detection of THz beating + THz generation
Appl. Phys. Lett. 89, 201101 (2006)
Experiments(detection)
Simulation(generation+detection)
Frequency (GHz)
⟨VDS⟩
δ VDS
Resonant frequency vs swing voltage
3f0
f0
5f0
Provides frequency tuningIEEE J. Sel. Top. Quant. Electron. 14,
491 (2008)
Enhancing detection
Experiments
Simulation
Journ. Appl. Phys. 106, 013717 (2009)
Modeling
THz imaging with HEMT
Non resonant detection
F. Teppe et al., to be published (2009)
Summary of plasma waves nanotransistors
Detector/EmitterRoom temperatureFrequency tuning
Integration
Emission mechanism?
Power?
2. TeraHertz MASER
… or exploiting the optical-phonon transit-time resonance in nitrides
Scattering rates in GaN at T=10 K
J. Appl. Phys. 89, 1161 (2001)
low energies: acoustic and impurity scatteringhigh energies: optical phonon emission
The optical-phonon transit-time resonance
Energy
acceleration τE
optical
phonon
Sca
tteri
ng
rate
τ -
τ +
τ- : Average relaxation timeτE : Carrier transit time τ+ : Time for optical phonon emission
Advantages of nitrides
Stronger electron-phonon couplingMuch sharper threshold
J. Appl. Phys. 89, 1161 (2001)
InN, T=10 K
InN, T=10 K
InN, T=10 K
InN, T=10 K
Summary of amplification bands
Phys. Rev. B 76, 045333 (2007)
Design of a cavity and emitted power
Gain depends on the electric field
large E
low E
Summary of TeraHertz MASER
SimpleFrequency tuningHigh amplificationNo magnetic field
77 KHigh quality
materialHigh field
Conclusions• Exciting field for theory and experiments
• Junction electronics/optics
• New phenomena, materials, devices, systems
Sujet de stage
« Etude expérimentale des oscillations Gunn et de plasma
téraHertz dans des composants de la micro-électronique »