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Novel InSb-based Quantum Well
Transistors for Ultra-High Speed,
Low Power Logic Applications
Suman Datta and Robert Chau
Intel Corporation, USA
In collaboration with
QinetiQ, Malvern Technology Center, UK
QinetiQ Team
T. Ashley, A. R. Barnes, L. Buckle, A. B.
Dean, M. T. Emeny, M. Fearn, D. G.
Hayes,K. P. Hilton, R. Jefferies, T. Martin,
K. J. Nash, T. J. Phillips, W. H. A. Tang
and P. J. Wilding
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Outline
•
Introduction
•
InSb as High Mobility Channel Material
•
InSb Materials Growth and Results
•
InSb QW Transistor Fabrication
•
Device Characterization and Results
•
Benchmarking of InSb based Transistors to
Silicon based Transistors for Logic
Applications
Channel Material Properties at
295K
•
InSb shows the highest room temperature
mobility, but also the lowest energy band-gap
Si GaAs In.53Ga.47As InAs InSb
Electron Mobility (cm2V-1s-1) ns=1x1012/cm2)
600 4,600 7,800 20,000 30,000
Electron Saturation
Velocity (107cm/s) 1.0
1.2 0.8 3.5 5.0
Ballistic Mean
Free Path (nm) 28 80 106 194 226
Energy
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InSb Quantum Well Transistor and
Multi-layer Epitaxial Structure
Non Self-aligned Ohmic contacts
Schottky Barrier Metal
S.I. GaAs substrate for epitaxial growth
Remote Doping
Layers
High electron mobility InSb quantum well
Higher band-gap
matrix AlxIn1-xSb
for reduced junction leakage
metamorphic AlInSb buffer layer
Layer Material Thickness (nm)
Top Barrier Al
xIn1-xSb 15-45
Doping Te
-Spacer Al
xIn1-xSb 5
Channel InSb 20
Metamorphic
Buffer AlyIn1-ySb 3,000
Substrate GaAs
• Carriers are confined within the InSb quantum well for transport
Hall Mobility of Doped versus
Modulation Doped InSb Channel
• Thicker buffer layer improves InSb QW mobility
• Modulation doping with Al.15In.85Sb barrier layer improves mobility only at low carrier densities.
0 10000 20000 30000 40000
0 5E+11 1E+12 1.5E+12 2E+12
Sheet carrier density (cm-2)
Carrier mobility (cm
2 V -1 s -1 )
Doped Channel on 1 µm AlInSb buffer
Doped Channel on 3 µm AlInSb buffer
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Schrödinger Poisson Simulation of
Carrier Confinement in QW
0 20 40 60 80 100
Depth (nm)
Energy (eV)
0 20 40 60 80 100
Depth (nm)
Energy (eV)
15% Al barrier 30% Al barrier
Eo
E1
E1
Eo
• Higher conduction band offset barrier results in
Hall Mobility of Modulation Doped
InSb Quantum Well
Sheet carrier density (cm-2)
Carrier mobility (cm
2 V -1 s -1 )
0 10000 20000 30000 40000
0 5E+11 1E+12 1.5E+12 2E+12
Remote doped in 15% Al barriers
Remote doped in 20% Al barriers
Remote doped in 30% Al barriers
Bulk InSb (20nm well)
• Room temperature InSb QW mobility over 30,000 cm2V-1s-1
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InSb QW Transistor Fabrication
Gate
Drain Voltage, VDS(V)
Drain Current
(mA/
µ
m) VGS = 0 V
• A two gate finger InSb QW transistor (LG=200nm ) fabricated with gate air-bridge using mesa isolation
InSb QW Transistor DC
Gate voltage (V)
Drain and Gate Current (
mA
Drain Current Gate Current Gm
Gate voltage (V)
Drain and Gate Current (
mA
Drain Current
Gm
VDS=0.5, 0.05V
• Peak gm of 900 µS/µm is obtained with 200nm LG devices
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InSb QW Transistor High Frequency
Characteristics
fT = 150GHz
fmax ~ 190GHz
0 10 20 30 40
0.1 1 10 100 1000
Frequency (GHz)
Gain (dB)
h21
MSG/MAG
Ug
VDS = 0.5V, V GS = -0.4V
fT = 150GHz
fmax ~ 190GHz
fT = 150GHz
fmax ~ 190GHz
• Unity gain cut-off frequency, fT ~ 150GHz is achieved with 200nm LG InSb QW transistor
Performance and active Power
Dynamic Power Dissipation (µW/µm)
Cut-off Freque
ncy, f
Increasing VDS 1.2 V
1.0 V 0.7 V
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Gate Delay vs Gate Length
0.1 1 10 100
1 10 100 1000 10000
Gate Length, LG (nm)
Gate Delay, CV/I (ps)
Si MOSFETs
InSb QW Transistors
NMOS
• InSb QW transistors provide 5X improvement in intrinsic gate delay over Si transistors at similar LG
Conclusions
• Room temperature mobility of 30,000 cm2V-1s-1 has
been achieved with InSb quantum well.
• InSb QW transistors are demonstrated to operate in depletion mode at 0.5V VDS (0.5V VGS swing), with an Ion-Ioff ratio ~ 80 and fT ~ 150 GHz
• InSb QW transistors (LG = 200nm) show equivalent high frequency performance as Si transistors (LG = 80nm) with 10X lower active power dissipation
• Schottky gate leakage sets the Ioff limit for the InSb QW transistors
