40 GHz MMIC Power Amplifier in InP DHBT Technology

Y.Wei, S.Krishnan, M.Urteaga, Z.Griffith, D.Scott,

V.Paidi, N.Parthasarathy, M.Rodwell

Department of Electrical and Computer Engineering, University of California

yunwei@ece.ucsb.edu tel: 805-893-8044, fax 805-893-3262

OutlineLEC 2002 UCSB

• Introduction• Transferred-Substrate Power DHBT Technology• Circuit Design• Results• Conclusion

Introduction LEC 2002

• Applications for power amplifiers in Ka band satellite communication systems wireless LANs local multipoint distribution system

personal communications network links and digital radio

• MMIC Amplifiers in this frequency band

Kwon et. al., IEEE MTT, Vol.48, No. 6, June. 2000

3 stage HEMT, class AB, Pout=1 W, Gain=15 dB, PAE=28.5%, size=9.5 mm2

• This Work:

Single stage cascode InP DHBT, class A, Pout=50 mW, Gain=7 dB, PAE=12.5% size=0.42 mm2

Transferred-Substrate HBT MMIC fabrication

MBE DHBT layer structure

Band profile at Vbe=0.7 V, Vce=1.5 V

InP 8E17 Si 300 Å

emitter

InGaAs 1E19 Si 500 Å

Grade 1E19 Si 200 Å

InP 1E19 Si 900 Å

Grade 8E17 Si 233 Å

Grade 2E18 Be 67 Å

InGaAs 4E19 Be 400 Å

Grade 1E16 Si 480 Å

InP 2E18 Si 20 Å

InP 1E16 Si 2500 Å

Multiple stop etch layers

Buffer layer 2500 Å

base collector

substrate

400 Å InGaAs base3000 Å InP collector

0

10

20

30

40

1 10 100 1000

Gai

ns (

dB)

Frequency (GHz)

U

h21 462

395

343

139

Small-area T.S. DHBTs have high cutoff frequencies.

UCSBSangmin Lee

0.0

1.0

2.0

3.0

0 1 2 3 4 5 6 7 8 9

Vce(V)

Ic(m

A)

BVCEO = 8 V at JE =0.4 mA/m2

fmax = 462 GHz, ft = 139 GHz

Vce(sat) ~1 V at 1.8 mA/m2

Design difficulties with large-area power DHBTs UCSBYun Wei

ARO MURI

Thermal instability further increasescurrent non-uniformity

Ic

Temperature

collector

SiNemitter

contactbase poly

BCBBCB Metal strip

Au Via

Steady state current and temperature distribution when thermally stable

base feed sheet resistance:

s= 0.3 / �significant for > 8 um emitter finger length

Large Area HBTs: big Ccb, small Rbb,

even small excess Rbb

substantially reduces fmax

0.08 m

Emitter contactMetal1

Base contact

Current hogging in multi-finger DHBT:

Distributed base feed resistance:

Ic

Temperature

K<1 for thermal stability→ must add emitter ballast resistance

Initial current and temperature distribution

thermal feedback further increases current non-uniformity

8 finger common emitter DHBTEmitter size: 16 um x 1 um Ballast resistor (design):9 Ohm/finger

0

20

40

60

80

100

120

0 1 2 3 4 5

I c, m

A

Vce

, Volts

Ibstep = 380 A

0

5

10

15

20

25

0 1 2 3 4 5 6

I c, m

A

Vce

, Volts

Ibstep = 300 A

0

5

10

15

20

25

1010 1011

Ga

ins,

dB

Frequency, Hz

H21

U

fmax

=120 GHz

f=91 GHz

Jc=5e4 A/cm2

Vce=1.5 V

First Attempt at Multi-finger DHBTs: Poor Performance Due to Thermal Instability

thermally driven current instability collapse

UCSB

low fmax due to premature Kirk effect (current hogging) excess base feed resistance

ARO MURI

Yun Wei

Large Current High Breakdown Voltage Broadband InP DHBT

UCSB

8 -finger DHBT8 x (1 m x 16 m emitter )8 x (2 m x 20 m collector )

Key Improvements8 Ohm ballast per emitter finger2nd-level base feed metal

Device Performancefmax>330 GHz, Vbrceo>7 V,Jmax>1x105 A/cm2

100 mA, 3.6 Volt device

2nd-level base feed metal

Ballast resistor

emitter

collector

Flip chip

Yun Wei

ARO MURI

UCSBHBT power amplifier-why cascode?

ARO MURI

Yun Wei

IB1

* R. Ramachandran and A.F. Podell "Segmented cascode HBT for microwave-frequency power amplifiers"

Advantages:common-base stage has large Vce

→ large output power common-emitter-stage has low Vce

→ small Rballast required

→ maintains large available power gain

Disadvantageinductance of base bypass capacitoreven small L greatly degrades gain

Vce1

Vce2

+-+

-IE1

Rballast

IE2

radial stub capacitor

common basestage mesa

common emitterstage mesa

bias 2 bias 3

bias 1

UCSBInP TS DHBT Power Amplifier Design

ARO MURI

Yun Wei

Optimum admittance match

Input match

Low frequency stabilization

4 parallel cascode amplifier

4 parallel cascode amplifier

8 finger cascodeInter-stage

DC bias

/4

/4

Imax

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0

Vce (V)

0.000

0.002

0.004

0.006

0.008

0.010

0.012

0.014

0.016

0.018

Ic (

A)

VCE_BRVsat

40 GHz 128 m2 power amplifier UCSB

cascode PA

0.6mm x 0.7 mm, AE=128 m2

ARO MURI

f0=40 GHz

BW3dB=16 GHz

GT=7 dB

P1dB=14 dBm

Psat=17 dBm @ 4dB gain

-40

-30

-20

-10

0

10

20 25 30 35 40 45

Sij,

dB

Frequency, GHz

S21

S11

S22

-5

0

5

10

15

20

0

2

4

6

8

10

12

14

-15 -10 -5 0 5 10 15

Po

ut,

GT,

dB

m

PA

E, %

Pin, dBm

GT

Pout

PAE

Yun Wei

UCSBYun Wei

common base PA

-5

0

5

10

15

20

0

2

4

6

8

10

-15 -10 -5 0 5 10 15

Po

ut,

dB

m GT , d

B

Pin, dBm

GT Pout

-30

-25

-20

-15

-10

-5

0

5

10

80 90 100 110

S11

, S

21,

S22

frequency, GHz

S21

S22

S11

0.5mm x 0.4 mm, AE=128 m2

ARO MURI

Bias: Ic=78 mA, Vce=3.6 V

f0=85 GHz

BW3dB=28 GHz

GT=8.5 dB

P1dB=14.5 dBm

Psat=16dBm, associated gain: 4.5 dB

Y. Wei et al, 2002 IEEE MTT-S symposium

W band power amplifiers in TS InP DHBT technology

W band power amplifiers in TS InP DHBT technology

UCSBYun Wei

cascode PA

0.5mm x 0.4 mm, AE=64 m2

ARO MURI

-5

0

5

10

15

0

2

4

6

8

10

-15 -10 -5 0 5 10

Po

ut, d

Bm G

T , dB

Pin, dBm

GT Pout

Bias: Ic=40 mA, Vce=3.5 V

f0=90 GHz

BW3dB=20 GHz

GT=8.2 dB

P1dB=9.5 dBm

Psat=12.5 dBm, associated gain: 4 dB

Y. Wei et al, 2002 IEEE MTT-S symposium

Continuing work

Higher-current DHBTs for increased mm-wave output power250 GHz fmax, Ic,max=240 mA, thermally stable at 200 mA bias at Vce=3.2 Volts→ suitable for W-band ~150 mW power amplifiers

W-band DHBT power amplifiersdesigns for > 100 mW saturated output power now being tested

Results to be reported subsequently…

UCSB

Yun WeiLEC 2002

Conclusions

• 40 GHz MMIC power amplifier in InP DHBT technology

7 dB power gain and 14 dBm output power at 1 dB compression. 17 dBm (50 mW) saturated output power 12.5% peak power added efficiency

Future work: higher power DHBT power amplifiers at W-band and above

lumped 4-finger topology, longer emitter fingers, power combining

G-band (140-220 GHz) DHBT power amplifiers

Acknowledgement

Work funded by ARO-MURI program under contract number PC249806.

UCSB

Yun WeiLEC 2002