Junction barrier effects on the microwave power performance of double heterojunction bipolar transistors

The barrier effects in InP based double heterojunction bipolar transistors have been investigated both theoretically and experimentally. It was found that the gradual saturation of collector current with increasing collector voltage was caused by the collector-base heterojunction barrier. The gain compression with increasing base current was caused by electron accumulation at the collector-base heterojunction. These effects have been included in terms of nonlinear currents and capacitances in an equivalent circuit model for the prediction of DHBT large signal performance. By using an InAlAs emitter and an InP collector with an InGaAs spacer to alleviate these undesirable effects, improvement in microwave power performance was verified