Transcript Physical Mechanisms for TeraHertz Electronic Devices

Physical Phenomena
for TeraHertz
Electronic Devices
Jérémi TORRES
Institute of Electronics of the South
University Montpellier
France
Outline
•
TeraHertz : Generalities
•
Physical phenomena
1. Plasma-waves
2. Optical-phonon resonance
3. Conclusions
The High-Frequency Investigation
Group
Microwaves
Theory
Experiments
Antennas/Radars
EM Compatibility
RFID
Monte Carlo
Hydrodynamic
Drift-Diffusion
Photoexcitation
THz devices
Near-field
EM cartography
The TeraHertz “gap”
f = 1012 Hz, 300 GHz - 10 THz, λ = 1 mm - 30 μm
Electronics
Photonics
Low cost
Compact
Room temperature
Continuous-wave
Tunable
Integration
Power vs frequency
Proc. of IEEE 23, 10
Optical THz Devices
Indirect
•
•
Direct
Laser Beating +
photoconductor
• Gas laser
Femtosecond laser +
nonlinear cristal
• p-Ge laser
• Free electron laser
• Quantum cascade laser
Difficulties:
complexity, cost, magnetic field, maintenance,
temperature
Electronic THz Devices
Direct
Indirect
•
•
Multiplication
Nonlinearities
• Gunn, RTD, Impatt diodes
• Schottky, varactor diodes
• Magnetron, Carcinotron
• FETs, HEMTs
Difficulties:
current, temperature, contact resistance, efficiency,
noise
Main Features of THz
Radiation
• Non ionizing
• Strong interaction with molecules
• Transmitted through many materials
• Higher resolution than microwaves
Applications in Spectroscopy
Physics: 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 Spectroscopy
Astronomy: atmospheric window, detection of
molecules, atoms, ionized gas
Applications in
Telecommunications
TeraHertz
antennas, wireless communication
Progr. Quant. Electr. 28, 1
Applications in Art
http://www.spiegel.de
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)
Applications in Imaging (T-Ray)
Courtesy of Teraview
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 oscillato
Practical applications :
High Electron Mobility
Travelling plasma waves
vdriftvplasma
vdrift+vplasma
Travelling plasma waves
Mascaret over the Dordogne river
http://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
ppl. Phys. Lett. 89, 201101 (2006)
THz
beating
Detection of THz beating + THz generation
Experiments
(detection)
Appl. Phys. Lett. 89, 201101 (2006)
Simulation
(generation+detection)
δ VDS
⟨VDS⟩
Frequency (GHz)
Resonant frequency vs swing
voltage
5f0
3f0
f0
Provides frequency tuning
IEEE J. Sel. Top. Quant. Electron. 14, 491
Enhancing detection
Simulation
Experiments
Modeling
Journ. Appl. Phys. 106, 013717 (2009)
THz imaging with HEMT
Non resonant detection
F. Teppe et al., to be published (2009)
Summary of plasma waves
nanotransistors
Detector/Emitter
Room temperature
Frequency 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
low energies: acoustic and impurity scattering
high energies: optical phonon emission
. Appl. Phys. 89, 1161 (2001)
The optical-phonon transit-time resonance
Scattering
rate
τ
τ
-
acceleration
τE
Energy
τ- : Average relaxation time
τE : Carrier transit time
τ+ : Time for optical phonon emission
+
optical
phono
n
Advantages of nitrides
Stronger electron-phonon coupling
Much 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
low E
large E
Gain depends on the electric field
Summary of TeraHertz MASER
Simple
Frequency tuning
High amplification
No magnetic field
77 K
High quality material
High 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 »