GaN MMIC PAs for MMW Applicaitons
Miroslav Micovic
HRL Laboratories LLC,
3011 Malibu Canyon Road, Malibu, CA 90265, U. S. A.
mmicovic@hrl.com
© 2008 HRL Laboratories, LLC. All Rights Reserved
Motivation for High Frequency Power sources
60 GHz – 110 GHz Frequency Spectrum
High Data Rate Wireless Links (10 Gbits/s)
Commercial Bands (E-band radio)
71 GHz – 76 GHz, 81 GHz – 86 GHz, 92 GHz – 95 GHz
Inter-Satellite
59.3 GHz – 64 GHz
Active Millimeter-Wave Imaging
94 GHz SAR, Phase Array Radar
(Space based W-band radar for earth studies.)
RF Sources for THz Multiplier Diodes
Fundamental Power for THz Space Array
Spectroscopy
Power Required ≈ Watts
Available Sources < 200 mW
GaN MMIC ≈ 3 W at 95 GHz
© 2008 HRL Laboratories, LLC. All Rights Reserved
Microwave and Millimeter-wave
Solid State Sources
1000
Pulsed mode
Estimated CW GaN limit
Pout [W]
100
Estimated CW LDMOS limit
10
Estimated CW GaAs limit
HRL GaN 2008
Symbols:
LDMOS catalog items
GaAs catalog items
GaN reported data
1
HRL GaN 2007
HRL GaN 2006
0.1
0.1
1
10
Frequency [GHz]
Output power per single die.
© 2008 HRL Laboratories, LLC. All Rights Reserved
100
HRL W-band GaN Roadmap
Extrapolate
Extrapolate>3
>3W!
W!
Output Power (mW)
3,500
3,000
Q3
Q32008
2008
Plan
Plan
2,500
2006
2006HRL
HRL
IEDM
IEDMpaper
paper
2,000
1,500
1,000
HRL
HRLIR&D
IR&D
2007
2007
500
Q4
Q42008
2008
Plan
Plan
0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
Best
BestGaAs
GaAs
pHEMT
pHEMT
and
1.8
andInP
InPHEMT
HEMT
Gate Width (mm)
DisruptiveW-band
W-bandGaN
GaNPower
PowerMMICs
MMICs
Disruptive
8Xhigher
higherpower
powerdensity
densitythan
thanmmW
mmWGaAs
GaAspHEMT
pHEMT
8X
© 2008 HRL Laboratories, LLC. All Rights Reserved
Cost trade-off estimate for 3 Watt W-band SSPA
GaAs pHEMT SSPA
GaN SSPA
8-way waveguide
combining
8-way splitter and 8 way
combiner required
Power combining not
required
Number of WR-10 power
modules
8
1
Number of MMIC’s per
module
3 (Attenuator, Phase
Shifter, Power Amplifier)
1 (Power Amplifier only)
Hand-tuning to obtain
phase and amplitude
match for combining
Combiner arms tuned
manually
No tuning
Watt95
95GHz
GHzGaN
GaNSSPA
SSPAisisCost
CostEffective
Effective
33Watt
© 2008 HRL Laboratories, LLC. All Rights Reserved
W-band GaN MMIC Device
T-gate device
Passivation
Lg = 0.12 µm
Low ohmic contact resistance < 0.2 Ω/mm.
Gate
Source
Ohmic
n+GaN
Comparable to GaAs pHEMT’s and InP HEMT’s.
Drain
Ohmic
n+GaN
Smooth ohmic metal edges.
Recessed gate
Bi-layer e-beam gate litho
AlGaN Schottky barrier
Lg = 0.12 µm for Ka-band
GaN
SiN passivation and capacitor dielectric
AlGaN buffer
2 µm Source-Drain separation
SiC substrate
TaN 50 Ω/Square resistor
Epi resistors
N+ layer facilitates fabrication of ohmic
contacts. Double Heterojunction Structure
© 2008 HRL Laboratories, LLC. All Rights Reserved
Short Channel Effects - Buffer Isolation
10
Ef
0
-1
18
16
10
Al
Ga
0.26
N
0.74
GaN
14
10
-2
12
10
-4
10
0
200
400
600
800
Position [Angstroms]
10
1000
Ec
1
18
10
Ef
0
1016
-1 Al0.3Ga0.7N
GaN
Al
Ga
0.04
14
10
-2
12
10
-3 Ev
-4
10
0
200
400
600
800
Position [Angstroms]
Techniques used to improve backside confinement and buffer isolation
Doping
– Fe doped buffer layer; Y.-F. Wu et al., El. Dev. Lett., Vol. 25, pp 117-119
– C doped buffer layer; S. Rajan et al., El. Dev. Lett., Vol. 25, pp 247-249
Polarization Engineering
– GaN DHFET structure; M. Micovic et al., IEDM 2004 Digest, pp 807-810
– InGaN back barrier; T. Palacios et al., El. Dev. Lett., Vol. 27, pp 13-15
© 2008 HRL Laboratories, LLC. All Rights Reserved
N
0.96
-3
-3 Ev
-3
Electrostatic Potential [eV]
1
Electron Concentration [cm ]
Ec
10
20
10
Electron Concentration [cm ]
2
DHFET
2
20
Electrostatic Potential [eV]
Conventional
SHFETHEMT
10
1000
Short Channel Effects - Buffer Isolation
Transfercurves
curves ofof
GaN
(blue)
SHFET
(red);
Transfer
LgDHFET
= 0.12
µmand
GaN
HEMTs
Both wafers have field plate gate structure; Vds=10V
Conventional (Red), DHFET (Blue)
10000
1000
Ids [mA/mm]
100
Vds=10V
10
>1000x
Leakage
Reduction
1
0.1
Ids DHFET
Idss SHFET
0.01
0.001
-5
-4
-3
-2
-1
Vg [V]
DHFET Structure:
-Improved Back-Channel Confinement,
-Reduced sub-threshold drain leakage current.
© 2008 HRL Laboratories, LLC. All Rights Reserved
0
1
2
Uniformity Better than 1% over 3” Wafer
Epi Thickness 0.90 %
AlGaN % 0.68 %
Uniformity = Std. Dev. / Mean No edge exclusion
© 2008 HRL Laboratories, LLC. All Rights Reserved
Sheet resistance 0.46 %
Individual Source Vias
• 30x30 vertical wall vias in 50 µm substrate
• Enables microstrip MMICs
• Low source inductance < 10 pH
– Critical for high power W-band power amp performance
© 2008 HRL Laboratories, LLC. All Rights Reserved
DC Device Characteristics
Lg = 0.1 µm, Wg = 4 x 37.5 µm GaN HFET
Vgs = 0 to -4 V
500
Ids
gm
900
Step = -0.5 V
100
80
60
800
-1.0 V
700
350
-1.5 V
600
300
500
250
400
200
-2.5 V
300
150
-3.0 V
200
100
100
50
-2.0 V
40
20
0
0
2
4
6
8
Vds [V]
10
450
-0.5 V
Ids [mA/mm]
120
Id [mA]
1000
Vgs =0
12
14
0
-4.5
400
0
-4
-3.5
-3
-2.5
-2
-1.5
Vgs [V]
Idss = 900 mA/mm
© 2008 HRL Laboratories, LLC. All Rights Reserved
gm of 360 mS/ mm
at Vds = 12 V
-1
-0.5
0
gm [mS/mm]
140
Small Signal RF Performance
35
fT
30
MSG
H21
Gain [dB]
25
= 90 GHz
fmax = 200 GHz
20
15
10
5
0
1
10
100
Frequency [GHz]
Lg = 0.1 µm, Wg = 4 x 37.5 µm GaN HFET Vds = 10 V, Ids = 45 mA.
© 2008 HRL Laboratories, LLC. All Rights Reserved
500 mW 70 GHz GaN MMIC PA
70 GHz MMIC Chip Layout
Size 3.4 mm x 1.3 mm
Operating Voltage = 15 V
Measured Gain > 15 dB
Small Signal Gain, Return Loss [dB]
20
12 GHz Measured
Bandwidth,
Gain >response
15 dB,ofGain
Ripple
0.5 dB
frequency
70 GHz
GaN<PA
82.3 GHz
16.16 dB
70.04 GHz
15.46 dB
10
71.02 GHz
15.42 dB
76.13 GHz
16.29 dB
0
-10
-20
60
70
80
90
Frequency (GHz)
Measured small signal gain of 70 GHz 500 mW GaN MMIC PA.
Performancemeets
meetsdesign
designgoal.
goal.
Performance
© 2008 HRL Laboratories, LLC. All Rights Reserved
Output power of 70 GHz MMIC measured at
a frequency of 76 GHz
Pout (dBm), Gain (dB), PAE (%)
30
Pout (dBm)
Gain (dB)
PAE (%)
25
20
15
10
Psat = 500 mW
PAE = 17%
P1dB = 24 dBm
Vds = 15 V
5
0
0
1
2
3
4
5
6
7
8
Pin (dBm)
© 2008 HRL Laboratories, LLC. All Rights Reserved
9
10 11 12 13 14 15
Comparison of 70 GHZ MMIC Performance
with the best commercial pHEMT
Parameter
70 GHz GaN
MMIC PA
Commercial
GaAs pHEMT
Gain
>14 dB
> 5 dB
P1dB
24 dBm
20 dBm
Psat
27 dBm
22 dBm
PAE
16.5 %
Input return
loss
< -8 dB
< -4 dB
Output return
loss
< - 8 dB
< -2 dB
Themost
mostpowerful
powerfulMMIC
MMICreported
reportedto
todate
dateat
at70
70GHz
GHz
The
© 2008 HRL Laboratories, LLC. All Rights Reserved
500 mW 80 GHz GaN MMIC PA
15 GHzfrequency
Bandwidth,
Gain
> 11
dBGaN PA
Measured
response
of 80
GHz
80 GHz MMIC Chip Layout
Size 3.4 mm x 1.3 mm
Operating Voltage = 15 V
Measured Gain > 11 dB
Small Signal Gain, Return Loss [dB]
20
10
76.37 GHz
14.97 dB
82.721 GHz
14.5 dB
86.062 GHz
12.07 dB
0
-10
-20
60
70
80
Frequency (GHz)
90
100
Measured small signal gain of 80 GHz 500 mW GaN MMIC PA.
MMICDesigned
Designedfor
forE-band
E-bandRadio
RadioBand
Band
MMIC
© 2008 HRL Laboratories, LLC. All Rights Reserved
Output power of 80 GHz MMIC measured at
a frequency of 83 GHz
Pout , Gain, PAE [dBm, dB, %]
30
27 dB m
P out
G a in
PAE
25
20
17 %
15
12 dB
10
Psat = 500 mW
PAE = 17%
P1dB = 24 dBm
Vds = 15 V
5
0
-1 0
-5
0
5
10
15
Power modules
using 2006 GaN SR
parts used as a
power source.
20
P in [d B m ]
HighestOutput
OutputPower
Powerand
andEfficiency
Efficiencyreported
reported
Highest
foraasolid
solidstate
statesource
sourceat
atthis
thisfrequency.
frequency.
for
© 2008 HRL Laboratories, LLC. All Rights Reserved
Comparison of 80 GHZ MMIC Performance
with the best commercial pHEMT
Parameter
80 GHz GaN
MMIC PA
Commercial
GaAs pHEMT
Gain
>11 dB
> 5 dB
P1dB
24 dBm
20 dBm
Psat
27 dBm
22 dBm
PAE
17 %
Input return
loss
< -7 dB
< -4 dB
Output return
loss
< - 7dB
< -2 dB
Themost
mostpowerful
powerfulMMIC
MMICreported
reportedto
todate
dateat
at80
80GHz
GHz
The
© 2008 HRL Laboratories, LLC. All Rights Reserved
500 mW 90 GHz GaN MMIC PA
Flat Response over 92 GHz- 95 GHz frequency band.
9 GHz
Bandwidth,
< -10
dBPA
Measured
frequency Return
response Loss
of 95 GHz
GaN
90 GHz MMIC Chip Layout
Size 2.4 mm x 1.3 mm
Operating Voltage = 15 V
Measured Gain > 15 dB
Small Signal Gain, Return Loss [dB]
20
90.884 GHz
14.88 dB
10
88.865 GHz
14.52 dB
97.451 GHz
14.22 dB
0
-10
-20
80
90
100
110
Frequency (GHz)
Measured small signal gain of 90 GHz 500 mW GaN MMIC PA.
Performance Meets Design Goals
© 2008 HRL Laboratories, LLC. All Rights Reserved
Output Power of 90 GHz GaN MMIC
measured at a frequency of 94.75 GHz
Pout , Gain, PAE [dBm, dB, %]
25
23 d B m
P o u t [d B m ]
G a in [ d B ]
P A E [% ]
20
15
1 3 .8 d B
10
P0.5dB = 23 dBm
Linear Gain = 14.4 dB
9 %
5
0
-2
0
2
4
6
8
10
P in [d B m ]
Output power limited by available input drive, circuit less than 0.5 dB compressed.
HRL is building a power source using GaN MMIC to test the power.
© 2008 HRL Laboratories, LLC. All Rights Reserved
Comparison of 90 GHZ MMIC Performance
with best commercial GaAs pHEMT
Parameter
HRL 90 GHz GaN
MMIC PA
GaAs pHEMT
Gain
>14 dB
> 10 dB
Gain Ripple
< 0.5 dB
< 1 dB
P1dB
>23 dBm
20 dBm
Psat
To be measured
23 dBm
PAE
To be measured
Input return
loss
< -10 dB
< -8 dB
Output return
loss
< - 10dB
< -8 dB
© 2008 HRL Laboratories, LLC. All Rights Reserved
250 mW 100 GHz GaN MMIC PA
Measured frequency response of 100 GHz GaN PA
100 GHz MMIC Chip Layout
Size 2.4 mm x 1.3 mm
Operating Voltage = 15 V
Measured Gain > 15 dB
Small Signal Gain, Return Loss [dB]
20
10
102.13 GHz
15.23 dB
95.912 GHz
15.19 dB
100.03 GHz
15.72 dB
0
-10
-20
80
90
100
110
Frequency (GHz)
Measured performance of the first 100 GHz GaN MMIC chip.
FastestGaN
GaNMMIC
MMICCircuit
Circuit
Fastest
NearTerm
TermPotential
Potentialfor
for150
150GHz
GHz––220
220GHz
GHz
Near
© 2008 HRL Laboratories, LLC. All Rights Reserved
Summary
• GaN MMIC technology will dominate high frequency > 50 GHz solid state RF power
technology.
• Key challenges for MMW GaN:
–
–
–
Ohmic Contacts
Short gate lengths
Device Structure
• GaN MMICs exceeding power of best GaAs and InP MMICs at 95 GHz demonstrated.
• GaN MMICs with 5 x power of the best InP MMICs are on the road map for 2009.
MMW GaN MMIC technology enables new systems, applications and services.
© 2008 HRL Laboratories, LLC. All Rights Reserved