Microwave Microelectronics Laboratory
Department of Electrical Engineering, USC
Research Focus:
- Wide Bandgap Microwave Power Devices and Integrated Circuits
- Physics, Simulation, Design and Characterization
The research in the Microwave Microelectronic Lab is focused on high power high frequency devices and ICs made of GaN and
related wide bandgap semiconductors. These devices are capable of delivering record high power density, operating in a broad
temperature range from cryogenic up to at least 300 C; they are robust and chemically stable. These features make GaM microwave
devices best candidates to replacing many of existing components, from Si devices in power conversion systems to MEMS in
microwave switches.
The group has demonstrated low loss high power microwave switches, power limiters and other devices and ICs which outperform
most of existing traditional devices. The group also works on GaN based components for power electronic applications.
III-Nitride microwave switches
Grigory Simin
Department of Electrical Engineering, University of South Carolina, Columbia, SC
simin@cec.sc.edu
1
Microwave switch applications
Microwave switches are
essential components in
nearly any modern RF
and microwave systems
Receiver
Transmitter
Microwave switches in 3G
cell communications
Microwave switches in
iPad
Satellite communications
with on-board switching
systems
Switch
Transmitter-receiver
switches in radars
Reconfigurable
phase-shifters in
phased-array
antennas
2
III-N HFET is a new paradigm in RF
switching
7
Ignoring the dislocation
array development
6
Critical barrier
thickness
5
4
AlGaN
GaN
5
1
nm
SiC
10
nm
2
3
AlGaN/GaN
heterostructure induces
303
4
nm
2
2DEG with sheet
densities up to 5×1013 cm-
1
2
0
0
0.2
0.4
0.6
0.8
Al Molar Fraction
1
forming metal-like
conducting plane
M. S. Shur, A. D. Bykhovski, R. Gaska, Sol.St. Elec., Vol. 44, pp. 205-210 (2000)
3
MOSHFET RF switch concept
S
D
G
VG
SiO2
S
AlGaN
G
D
FET
In p u t
GaN
O u tp u t
SiC
Vg
Ron
ON state
VG=0
Vg
Coff
OFF state
VG < VT
4
State-of-the-art III-N MOSHFET
S SiO2 G
D
AlGaN
GaN
SiC
Device component
AlGaN/GaN 2DEG:
µ ≅ 1800 cm2/V-s
nS ≅ 1.5 ×1013 cm-2
RSH ≤ 230 Ω/Sq.
Ω/
Insertion loss
5 µm S-D spacing, RSD ~ 1.15 Ω-mm ~ 0.1 dB-mm
~ 0.09 dB-mm
Contact RC ~ 0.5 Ω-mm
Total RON ~ 1.65 Ω-mm
~ 0.2 dB-mm
3-mm gate periphery MOSHFET
~ 0.065 dB
5
MOSHFET vs. other RF switching devices
Characteristic
Pin-diodes
RF MEMS
GaAs HEMTs
III-N
MOSHFETs
Technology
discrete
devices
Planar – IC
Planar - IC
Planar – IC
Insertion loss
0.3…1.5 dB
0.1…5 dB
0.2…2.5 dB
0.05…1.5 dB
Isolation
> 30 dB
> 40 dB
> 25 dB
> 30 dB
Handling
powers
< 10 W
<1W
<1W
Up to 100 W
Low
Low
Low
DC
power High
consumption
Biasing network
Requires LC Simple
filters
Simple
Low
Temperature,
chemical,
radiation
stability
Poor
Poor
Mediocre
Excellent
Reliability
Good
Mediocre
Good
Excellent
6
Typical circuit for low-loss high isolation
RF switch
Effect of RON and COFF on series/shunt RF switch
IC performance
D1
RF output
Z0=50Ω
RF input
Z0=50Ω
D2
RG1
RG2
V2
V1
Higher RON:
•
increases the insertion loss provided by the series device D1
•
decreases the isolation provided by the shunt device D2
Higher COFF:
•
increases the insertion loss provided by the shunt device D2
•
decreases the isolation provided by the series device D1
7
III-N Single-pole, single-throw (SPST)
switch MMIC
-10
Insertion loss (no metal loss)
Insertion loss (thin metal)
-0.2
-20
-0.4
-30
-0.6
-0.8
-40
Isolation
-1.0
0.5
1.0
1.5
Frequency (GHz)
Isolation (dB)
Insertion Loss (dB)
0.0
2.0
8
RF Transmission, dB
III-N Single-pole, double-throw (SPDT)
switch MMIC
0.0
-0.5
-1.0
-1.5
-2.0
-2.5
-3.0
-20
-30
-40
-50
-60
ON
OFF
0.5
1.0
1.5
2.0
Frequency, GHz
2.5
Insertion loss and isolation of III-Nitride
Single-pole double-throw integrated MOSHFET RF switch
9
III-N MOSHFET RF Switch maximum RF powers
IDS, A
2.0
1.5
1.0
VT - VG, V
0.5
75
50
25
0
20
ON
HP ADS simulations
Measured at 10 GHz
PON ~ IDS2×RL
OFF
HP ADS simulations
Measured at 10 GHz
2
POFF ~ (VG − VT ) / RL
25
30
35
40
45
Peak switching Power, dBm
50
10
Maximum switching power measured
MOSHFET
RF power is limited by the available power source
11
III-N MOSHFET RF Switch temperature stability
Isolation, dB
Insertion Loss, dB
0
-2
RT
100oC
200oC
-4
2
50oC
150oC
250oC
4
6
8
Frequency, GHz
10
0
-5
-10
-15
-20
-25
-30
-35
-40
RT
100oC
200oC
2
50oC
150oC
250oC
4
6
8
Frequency, GHz
10
Tested temperature range limited by the probe station specs
12
Resistance, Ω
35
30
Room temp.
25
20
15
Liquid N
10
5
0 2 4 6 8 1012141618202224
Electrode spacing
TLM data for MOSHFET RF switch at
77K and room temperature.
300K: Rsh=268 W/sq; Rc= 0.45 W×mm;
Transmission, dB
Cryogenic performance
0
-2
-4
-6
-8
-10
-12
-14
-16
1.0
ON (VG <VT)
RT
77K
OFF (VG = 0)
1.1
1.2
Frequency, GHz
1.3
Single shunt MOSHFET in a 50-W
CPW.
RF transmission at room temperature
and at 77K
77K: Rsh=92 W/sq Rc= 0.36 W×mm;
13
III-N MOSHFET RF Switch switching speed
DC (ON)
Pulsed
0.5
0.4
0.3
0.2
0.1
0.0
DC (OFF)
0
100
200
300
Time, nS
100 ns
pulses
DC (ON)
0.6
RF detector signal, a.u.
RF detector signal, a.u.
0.6
400
500
Pulsed
0.5
0.4
0.3
0.2
0.1
0.0
DC (OFF)
0
40
80
120
Time, µS
160
200
50 µs pulses
No large-signal RF dispersion (no current collapse)
Switching time is driver-circuit limited (ns range expected)
14
Millimeter-wave III-N C3-MOSHFET RF Switch
S
G
SiO2
D
S
G
SiO
SiO2
D
OUT
2
AlGaN
AlGaN
GaN
GaN
SiC
SiC/sapphire
SiC
• High-T annealing
C3 MOSHFET
• No annealed contacts
• Tight Gate alignment
• Alignment-free technology
Ohmic contacts
15
C3 HFET vs. regular HFET RF-switch
G
S
SiO
SiO22
RF Input
D
OUT
RF Output
AlGaN
GaN
SiC/sapphire
SiC
-10
VG = 0 (ON )
Transmission, dB
-1
-2
RF In
RF Out
-3
VG
-4
3HFET
-5
-6
C MOSHFET
HFET
MOSHFET
5
10
15
Frequency GHz
20
Transmission, dB
0
VG = -10 V
-15
(OFF)
-20
RF In
RF Out
-25
-30
VG
-35
HFET
C3MOSHFET
HFET
MOSHFET
-40
5
10
15
Frequency GHz
20
16
C3 MOSHFET RF Switch MMIC
VG1
L
DS
VG2
DP2
0
0
-5
-5
Insertion Loss
-10
-15
-20
Small-signal
-25
-30
-35
Isolation
1 2 3 4 5 6 7 8 9 10 11 12
Frequency (GHz)
Transmission (dB)
Insertion Loss & Isolation (dB)
DP1
-10
-15
-20
-25
-30
OFF
VG2=0
VG1=
-12V
-16V
-20V
ON
VG1=0
VG2=
-12V
-16V
10 GHz CW
-35
20 22 24 26 28 30 32 34 36 38 40
Pin (dBm)
17
Source
(RF in)
HfO2
AlGaN
GaN
2D gas
Drain
(RF out)
Gate
Insertion Loss, dB
C3 – HfO2 RF Switch
-2
-3
-4
-5
0
2
4
6
8
Frequency, GHz
10
5
Isolation, dB
0
-5
-10
-15
-20
HFET
MOSHFET
-25
-30
2
4
6
8
Frequency, GHz
10
A. Koudymov, N. Pala, V. Tokranov, S. Oktyabrsky, M. Gaevski, R. Jain, J. Yang, X. Hu, M. Shur, R. Gaska, G. Simin, HfO2
- III-Nitride RF Switch with Capacitively-Coupled Contacts, IEEE EDL, V. 30, Issue 5, pp:478 - 480 (2009)
18
Multigate C3- RF switches
Experimental multigate RF switch (W = 200 µm, LG = 0.25 µm)
Capacitively-coupled contacts (C3) – no annealed ohmic contacts
19
0
-1
-2
-3
-4
-15
Insertion Loss (1...4 gates)
-13
10 GHz isolation
Isolation (dB)
Insertion Loss / Isolation (dB)
Multigate C3- RF switches
-20
-25
Single Gate
2 Gates
4 Gates
-30
-35
-40
1
2
3
4 5 6 7 8
Frequency (GHz)
9
-15
-16
-17
-18
Dots - 2D simulations
-45
-14
10
1
2
3
Number of Gates
4
C3 multigate RF switch (W = 200 mm, LG = 0.25 mm)
G. Simin, B. Khan, A. Koudymov, M. Gaevski, R. Jain, J. Yang, X. Hu, R. Gaska, and M. Shur, GaN Multigate RF
Switches with Capacitively-Coupled Contacts. IEEE El. Dev. Lett, V. 30, N9 pp. 895-897 (2009)
20
Side-Gated C3 RF Switch
RF Input
ic
m
h
O es
r
d
3 o tro
C ec
el
Control
Control
RF Output
Control
C3
Control
C3
RF Input
RF Output
Control
C3
Control
C3
ic
m
h
O es
r
d
3 o tro
C ec
el
C3 electrodes
Channel
RF Input
RF Output
Substrate
No gate electrode in the RF Input-output region
Side-gate electrode controls the impedance of C3 contacts
thus turning switch ON and OFF
21
Side-gated C3- series test element
Control electrode
0
W=50 µm
Insertion Loss, dB
-1
C3 2um gap
-2
HFET
-3
-4
C3
-5
-6
W=50 um Series
ON
-7
-8
0
5
10
Frequency, GHz
Experimental data and comparison with C3 - models
22
Side-gated C3- SPST
Control electrode
RF input – output
interdigitated fingers
Single control electrode controls the ON/OFF state of the multi-finger C3-device
23
Side-gated C3- SPST performance
-10
0
-2
-4
Isolation,dB
Insertion Loss, dB
-15
0.3 dB @ 6 GHz
-6
-20
-25
-30
-35
MOS C3 SPST
-40
-8
-10
27.5dB @ 6 GHz
MOS C3 SPST
0
2
4
6
8
10
Frequency, GHz
-45
12
0
2
4
6
8
10
Frequency, GHZ
Small-signal insertion loss and isolation
Control electrodes bias
ON-state: VSER = 0; VSHT=10V;
OFF-state: VSER = 10V; VSHT=0;
12
24