Order-of-magnitude improvement in microwave power capacity of InGaP/GaAs HBT under isothermal pulsed operation

Order-of-magnitude improvement in power capacity was achieved in single-finger heterojunction bipolar transistors with sub-/spl mu/s pulses and less than 1% duty cycle, thereby approaching isothermal operation. At 6 GHz, the output power capacity was 14 mw//spl mu/m/sup 2/, which was much higher than the common benchmark of 1 mw//spl mu/m/sup 2/. The improvement in power capacity was found to be due to increased breakdown voltage as well as increased peak current under pulsed operation. The increased peak current was in turn due to a much higher Kirk threshold under isothermal operation.