A 25 GHz InGaAs/InAlAs-InP HBT power MMIC with 48% power added efficiency

This paper describes the first InAlAs/InGaAs-InP HBT MMIC power amplifier results reported for frequencies above 20 GHz. The MMIC amplifier employs a unique oval emitter array (OEA) device and a 1000 nm thick collector epitaxy in order to improve the thermal and electrical properties of the power HBT device cell. The resulting HBTs obtain a BV/sub ceo/ breakdown voltage of 8.5 V with f/sub T/'s and f/sub max/'s of 70 GHz and 120 GHz. The K-band MMIC amplifier combines four 2/spl times/5 oval emitter array devices (total area=286 um/sup 2/) using a compact four-way microstrip combiner and obtains an output power of 21.5 dBm, a power gain of 9.5 dB, and an associated power added efficiency of 48% at 25 GHz. These results were obtained at conservative peak current density of 23 KA/cm/sup 2/ and a low supply of 3.5 V which suggests reliable HBT power operation.