Common Base Amplifier with 7- dB gain at 176 GHz in InP mesa DHBT Technology V. Paidi, Z. Griffith, Y. Wei, M. Dahlstrom, N. Parthasarathy, M. Seo, M. Urteaga, M. J. W. Rodwell , Department of Electrical and Computer Engineering, University of California, Santa Barbara, CA 93106 L. Samoska, A. Fung, Jet Propulsion Labs, Pasadena, CA 91109

Outline Motivation. Why Common-base? Effect of layout parasitics on circuit stability and MSG. InP mesa DHBT process. Circuit simulations. Device Results G-band Power amplifier results. W-band Power amplifier results. First, I will explain briefly how class B power amplifier work and why single-ended Class B. Then I will talk about the design and simulation of the single ended class B power amplifier. Finally I will show you the measurement result and the conclusions.

Motivation and Previous Results Applications for electronics in 140-220 GHz frequency band Wideband communication systems Atmospheric sensing Automotive radar Small signal amplifier results 6.3 dB @ 175 GHz single stage amplifier in InP TSHBT technology, Miguel et.al., 12 dB @ 170 GHz three stage CE amplifier in InP TSHBT technology, Miguel et. al., 6-stage amplifier with 20  6 dB from 150-215 GHz, InP HEMT, Weinreb et. al. Power amplifier results 14-16 dBm @140-170 GHz with 10 dB gain in InP HEMT technology, Lorene et. al., 12.5 dBm @90 GHz with 8.6 dB gain in TS InP DHBT technology, Yun et. al., 14-16 dBm @65-145 GHz with > 10 dB gain in InP HEMT technology, Lorene et. al.,

Why mesa -InP HBTs for 140- 220 GHz power amplifiers ? fmax > 400 GHz, ft > 250 GHz High current density > 3 mA/ m2. Vbr,ce0 > 6V Low thermal resistance. High power density, high gain in 140-220-GHz frequency range

Why Common Base ? Common base has the highest MSG/MAG. Common Base Circuit Schematic Common base has the highest MSG/MAG.

Base inductance Ground 0.8 m base contact width emitter Ground Emitter access Interconnect metal Polyimide base 0.8m each 0.8 m base contact width Leads to base access inductance. Lb ~ 3 pH for 0.8 mX12 m HBT. Longer finger length results in larger base access inductance

Collector emitter overlap Capacitance reduction Double-sided collector Contact Single-sided collector Contact Single-sided Collector contact reduces Collector to emitter overlap capacitance

Cce, Lb degrade MSG/MAG Lb reduces MSG in 140-220-GHz frequency range.

Single-sided collector Contact improves MSG 2-3-dB improvement in MSG.

Mesa IC Process: overview Both junctions defined by selective wet-etch chemistry Low contact resistances NiCr thin film resistors s = 40  /  MIM capacitor, SiN dielectric. ADS momentum modeled CPW transmission lines Air bridges strap ground planes

Single-stage Common Base power amplifier Objectives: 180 GHz amplifier, Psat~ 20 dBm Approach: InP mesa-DHBTs Simulations: ADS S-parameter, harmonic balance and momentum simulations Circuit Schematic

Output Large-signal Load-line match (Simulations) Device Model Load-line match Circuit optimized for output power not gain

Single-stage Common Base power amplifier (Simulations) Frequency of operation =180 GHz 3-dB bandwidth = 45 GHz, Gain = 5.3 dB at 180 GHz, Pout,sat = 20 dBm. 2 x 2 x 0.8 m x 12 m, AE=38 mm2 5.3 dB at 180 GHz, 3-dB Bandwidth = 45 GHz, Saturated Pout, = 20 dBm

Two-stage Common Base amplifier Objectives: 180 GHz amplifier, Psat~ 20 dBm Approach: InP mesa-DHBTs Simulations: S-parameter and harmonic and momentum simulation in ADS Circuit Schematic

Two-stage Common Base amplifier (Simulations) Frequency of operation =180 GHz 3-dB bandwidth = 45 GHz, Gain = 8.7 dB, Pout,sat = 19.5 dBm. 6 x 0.8m x 12 m, AE=58 mm2 Power simulations at 180 GHz

Device Performance Vbr = 7 V. ft = 240 GHz, fmax = 290 GHz. DC characteristics of a 2 X 0.8 m X 12 m Common-base InP HBT RF characteristics of a 1 X 0.8 m X 8 m HBT biased at Jc= 3 mA/m2, Vce =1.7 V Vbr = 7 V. ft = 240 GHz, fmax = 290 GHz. Relatively lower fmax – larger base mesas relatively poorer base ohmics.

Power measurement setup 170-180 GHz Frequency doubler Power meter DUT W-band PA

Power measurement setup 150 GHz DUT Gunn Oscillator Calorimeter Var Attn

176 GHz single-stage Power amplifier 7- dB gain at 176 GHz. 3-dB bandwidth = 23 GHz. Pout = 8.7 dBm with 5 dB associated power gain at 172 GHz. 2 x 0.8m x 12 m, AE=20 mm2 Bias conditions Ic = 30 mA, Vcb= 1 V Power measurements at 172 GHz Bias conditions Ic = 40 mA, Vcb= 2 V

176 GHz single-stage Power amplifier At 172 GHz 7.53 mW output power with 5 dB associated gain. Maximum power measured = 8.37 mW at 176 GHz

176 GHz two-stage Power amplifier 7- dB gain at 176 GHz. Pout = 8.1 dBm with 6.3 dB associated power gain at 176 GHz. Saturated Pout = 9.1 dBm 4 x 0.8m x 12 m, AE=38 mm2 Power measurements at 176 GHz Ist stage Ic = 40 mA, Vcb= 2 V IInd stage Ic = 51 mA, Vcb= 1.8 V Ist stage Ic = 25 mA, Vcb= 1 V IInd stage Ic = 30 mA, Vcb= 1 V

176 GHz two-stage Power amplifier At 150.2 GHz 10.3 dBm Pout with 3.4 dB associated gain.

84 GHz single-stage Power amplifier 6.5- dB gain at 84 GHz. Pout = 32.4 mW with 4 dB associated power gain at 84 GHz. 4 x 0.8m x 12 m, AE=38 mm2 Power measurements at 84 GHz Bias conditions Ic = 56 mA, Vcb= 2.2 V Bias conditions Ic = 37 mA, Vcb= 1 V

Accomplishments Design and fabrication of W-band (75-110-GHz) G – band (140-220-GHz) power amplifiers in InP mesa DHBT technology 7-dB at 176 GHz with a single-stage common-base amplifier. Obtained 8.77dBm output power with 5-dB associated power gain at 172 GHz. Obtained 32 mW at 84 GHz. This work was supported by the ONR , JPL , DARPA (USA).