High-power, high-efficiency K-band AlGaAs/GaAs heterojunction bipolar transistors

We report on the state-of-the-art power performance of AlGaAs/GaAs HBTs at K-band. A prematched 12/spl times/(1.6/spl times/25) /spl mu/m/sup 2/ HBT unit cell exhibited 1.18 W CW output power (3.93 W/mm output power density) and 57.1% power-added efficiency with 6.6 dB associated gain at 20 GHz at a collector bias of 10.5 V. Peak power-added efficiency achieved was 57.8% at an output power level of 1.08 W. No intentional harmonic tuning was applied.