Design and fabrication of thermally-stable AlGaAs/GaAs microwave power HBTs

Record power density performance of AlGaAs/GaAs microwave power heterojunction bipolar transistors (HBTs) was accomplished through the use of novel design and fabrication techniques. Thermally-stable operation of HBTs up to their electronic limitation (10 mW/μm² output power density at 10 GHz with 0.6 W CW output power, 7.1 dB gain and 60% PAE) was attained. The design of the HBT was based on a detailed electro-thermal device analysis which revealed the necessity to provide an effective heat transfer path between heat sources in a multi-emitter power device. Excess heat was transferred out of the device using thermal shunt and thermal lens techniques. The thermal resistance of the device was lowered by a factor of 2.5-3 compared to conventional devices