Wband InPInGaAsInP DHBT MMIC Power Amplifiers

1
W-band InP/InGaAs/InP DHBT MMIC Power Amplifiers

• Yun Wei, Sangmin Lee, Sundararajan Krishnan,
  Mattias Dahlström, Miguel Urteaga, Mark Rodwell
• Department of Electrical and Computer
  Engineering, University of California

yunwei_at_ece.ucsb.edu tel [phone], fax
805-893-3262
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W-band MIMIC Power Amplifiers
IMS2002

• Y.C.Chen et. Al. IPRM, May 1999
• 2-stage 94 GHz W-band HEMT power amplifier
• 0.15 ?m composite-channel InP HEMT Imax750mA,
  VBR7V, Pout 316 mW
• J. Guthrie et. Al, IPRM, May 2000
• Cascode 78 GHz HBT power amplifier
• transferred substrate InGaAs/InAlAs SHBT
• Imax100mA, VBR2.5V, Pout 12 mW
• This work single stage W-band HBT power
  amplifiers
• transferred substrate InP/InGaAs/InP DHBT
  Imax128mA, VBR7V, Pout 40 mW
• Highest reported power for W-band HBT power
  amplifier

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Transferred-Substrate HBT MMIC technology

• HBT processing
• Normal emitter and base processing ? no
  collector contact
• polyimide isolation, SiN insulation,
  interconnection metals (M1 and M2),
  Benzocyclobutene planarization, thermal via and
  ground plane plating
• Flip chip bounding to carrier
• Substrate etching
• Schottky contact collector
• simultaneous scaling of emitter and collector
  widths ?
• Wiring environment
• Micro strip transmission line ? BCB dielectric,
  ?r2.7, t5 ?m
• MIM capacitors?BCB bypass capacitor, SiN
  capacitor (?r7, t0.4 ?m )
• NiCr resistor ? R40?/
• Low via inductance, reduced fringing fields,
  increased conductor losses

4
MBE DHBT layer structure
Band profile at Vbe0.7 V, Vce1.5 V
400 Å InGaAs base 3000 Å InP collector
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0.5 ?m Transferred-Substrate DHBT
UCSB
Sangmin Lee
fmax 462 GHz, ft 139 GHz
BVCEO 8 V at JE 0.4 mA/?m2
Vce(sat) 1 V at 1.8 mA/?m2
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UCSB
First Attempt at Multi-finger DHBTs Poor
Performance Due to Thermal Instability
ARO MURI
thermally driven current instability b
collapse
Jc5e4 A/cm2 Vce1.5 V
8 finger common emitter DHBT Emitter size 16 um
x 1 um Ballast resistor (design)9 Ohm/finger
low fmax due to premature Kirk effect
(current hogging) excess base feed resistance
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Multi-finger DHBTs Design Challenges
UCSB
ARO MURI
Thermal instability (current hogging) in
multi-finger DHBTs
Ic
Temperature
Thermal instability further increasescurrent
non-uniformity
Steady state current and temperature
distribution when thermally stable
Distributed base feed resistance
Self-aligned base contact thickness0.08 ?m base
feed sheet resistance ?s0.3 ?/ significant for
gt 8 um emitter finger length
Large Area HBTs big Ccb, small Rbb,
even small excess Rbb
substantially reduces fmax
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Large Current High Breakdown Voltage Broadband
InP DHBT
UCSB
ARO MURI
2nd-level base feed metal
8-finger device8 x ( 1 mm x 16 mm emitter )8 x
( 2 mm x 20 mm collector ) 7 ?m emitter
spacing 8 Ohm ballast per emitter
finger fmaxgt330 GHz, Vbrceogt7 V, Jmaxgt1x105
A/cm2
emitter
Flip chip
collector
Ballast resistor
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UCSB
DHBT large signal model Gummel-Poon model BC
parasitics thermal feedback
Gummel-Poon model from DC characteristics Base-
collector parasitics from measured
S-parameters Thermal effects modeled by
power-controlled base current Vbe variation,
using the measured thermal resistance
qta. Dynamic Load Lines Ammeter is internal
to Ccb optimum HBT load has zero phase angle
between ammeter and voltmeter
instant -aneous power
average power
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UCSB
Implementing the Thermal Feedback Large Signal
Model in Agilent ADS
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UCSB
Large signal DHBT model -Comparison of DC and RF
simulation and measurement
measured
simulation
U
h21
S21
S12
S11
S22
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UCSB
ARO MURI
InP TS DHBT Power Amplifier Design

• Designed using large signal model derived from
  DC-50 and 75-110 GHz measurements of previous
  generation devices
• Output tuning network loads the HBT in the
  optimum admittance for saturated output power
• Shunt R-C network at output provides low
  frequency stabilization
• Electromagnetic simulator (Agilents Momentum)
  was used to characterize passive elements

Low frequency stabilization
Input match
Optimum admittance match
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W band 128 mm2 power amplifier
UCSB
ARO MURI
common base PA
0.5mm x 0.4 mm, AE128 mm2
Bias Ic78 mA, Vce3.6 V
f085 GHz, BW3dB28 GHz,GT8.5 dB, P1dB14.5 dBm,
Psat16dBm
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W band 64 mm2 power amplifier
UCSB
ARO MURI
cascode PA
bias
0.5mm x 0.4 mm, AE64 mm2
Bias condition Ic40 mA, Vce_CB3.5 V,
Vce_CE1.5 V
f090 GHz, BW3dB20 GHz, GT8.2 dB, P1dB9.5 dBm,
Psat12.5 dBm
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Conclusions
UCSB
IMS2002

• Wideband Power DHBT Ic 100 mA, Vce3.6 V,
  fmax330 GHz thermal design and base feed design
  critical for wide bandwidth
• Power DHBT large signal modeling
• Wideband Power amplifiers f085 GHz, BW3dB28
  GHz,GT8.5 dB, Psat16dBm
• Future work
• Higher power DHBTs lumped 4-finger topology and
  longer emitter finger
• Multi-stage wideband power amplifiers
• 200 GHz power amplifiers
• Acknowledgement
• Work funded by ARO-MURI program under contract
  number PC249806.