Chau QWFET ICSICT foils 102004
®
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
(2)
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
QinetiQ, Malvern Technology Center, St.
Andrews Road, Malvern, WR14 3PS, UK
(3)
®
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
(4)
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
(5)
®
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
• InSb is embedded in a matrix of higher band-gap material, AlxIn1-xSb, to reduce leakage
(6)
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
(7)
®
Schrödinger Poisson Simulation of
Carrier Confinement in QW
0 20 40 60 80 100 -0.30
-0.20 -0.10 0.00 0.10 0.20 0.30
0 20 40 60 80 100
Depth (nm)
Energy (eV)
0 20 40 60 80 100 -0.30
-0.20 -0.10 0.00 0.10 0.20 0.30
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
increased confinement of electrons within the InSb QW at high carrier densities.
(8)
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
(9)
®
InSb QW Transistor Fabrication
Gate
Drain Source
Source
Gate
Drain Source
Source
0 0.05
0.1 0.15 0.2 0.25 0.3 0.35 0.4
0 0.2 0.4 0.6 0.8 1
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
• DC output characteristics show breakdown voltage above 1.2V
(10)
InSb QW Transistor DC
Characteristics
0.0001 0.001 0.01 0.1 11.2 -1 -0.8 -0.6 -0.4 -0.2 0
Gate voltage (V)
Drain and Gate Current (
mA /µm) 0 100 200 300 400 500 600 700 800 900 1000 Transc onductance (µ S/ µ m) Drain Current Gate Current Gm
VDS=0.5, 0.05V
0.0001 0.001 0.01 0.1 1
-1.2 -1 -0.8 -0.6 -0.4 -0.2 0
Gate voltage (V)
Drain and Gate Current (
mA /µm) 0 100 200 300 400 500 600 700 800 900 1000 Transc onductance (µ S/ µ m) Drain Current Gm
VDS=0.5, 0.05V
• Peak gm of 900 µS/µm is obtained with 200nm LG devices
• Schottky gate leakage limits the off-state leakage current
(11)
®
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
(12)
Performance and active Power
Trade-off
0 25 50 75 100 125 150 175
1 10 100 1000
Dynamic Power Dissipation (µW/µm)
Cut-off Freque
ncy, f
T
(GHz)
InSb
LG=0.2 µm
Silicon
LG= 80 nm
0.3 V 0.5 V
0.6 V
Increasing VDS 1.2 V
1.0 V 0.7 V
• InSb QW transistors provide equivalent high frequency performance as state-of-the-art Si transistors with 10X lower active power dissipation.
(13)
®
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
• Scalability of InSb QW transistors still remain to be demonstrated
(14)
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
• Future InSb-based transistors will require a) high-K dielectrics to reduce IG and b) enhancement mode operation to reduce IOFF for potential applications in ultra high speed, low power logic applications.
(1)
®
InSb QW Transistor Fabrication
Gate
Drain Source
Source
Gate
Drain Source
Source
0 0.05
0.1 0.15 0.2 0.25 0.3 0.35 0.4
0 0.2 0.4 0.6 0.8 1
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
• DC output characteristics show breakdown voltage
(2)
InSb QW Transistor DC
Characteristics
0.0001 0.001 0.01 0.1 11.2 -1 -0.8 -0.6 -0.4 -0.2 0 Gate voltage (V)
Drain and Gate Current (
mA /µm) 0 100 200 300 400 500 600 700 800 900 1000 Transc onductance (µ S/ µ m) Drain Current Gate Current Gm
VDS=0.5, 0.05V
0.0001 0.001 0.01 0.1 1
-1.2 -1 -0.8 -0.6 -0.4 -0.2 0 Gate voltage (V)
Drain and Gate Current (
mA /µm) 0 100 200 300 400 500 600 700 800 900 1000 Transc onductance (µ S/ µ m) Drain Current Gm
VDS=0.5, 0.05V
• Peak gm of 900 µS/µm is obtained with 200nm LG
devices
• Schottky gate leakage limits the off-state leakage
(3)
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
(4)
Performance and active Power
Trade-off
0 25 50 75 100 125 150 175
1 10 100 1000
Dynamic Power Dissipation (µW/µm)
Cut-off Freque
ncy, f
T
(GHz)
InSb
LG=0.2 µm
Silicon LG= 80 nm
0.3 V 0.5 V
0.6 V
Increasing VDS 1.2 V
1.0 V 0.7 V
• InSb QW transistors provide equivalent high frequency
performance as state-of-the-art Si transistors with 10X lower active power dissipation.
(5)
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
• Scalability of InSb QW transistors still remain to be
(6)
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
• Future InSb-based transistors will require a) high-K
dielectrics to reduce IG and b) enhancement mode
operation to reduce IOFF for potential applications in