Noise at high frequency operation of InP/InGaAs double heterojunction bipolar transistors

A theoretical study of the high-frequency noise characteristics of InP/InGaAs heterojunction bipolar transistors is carried out. The calculations take into account the high-frequency dependence of the base noise current and the correlation of different currents contributing to the collector noise current. The high current gain and the excess noise observed in the input noise current could cause some limitations for low-level wideband applications. Scaling the emitter size is required to reduce the excess high-frequency noise. This can be done in the InP/InGaAs system without degrading its performance due to the low surface recombination velocity. Very high DC current gain could reduce the bandwidth where the noise remains low.<>