Low frequency noise and microwave properties of InP/InGaAs heterojunction bipolar transistors

Recent progress in the growth and processing of InP-based heterostructures has led to the design of heterojunction bipolar transistors (HBTs) with typical cutoff frequencies in excess of 100 GHz and current gains of 50-100. Besides the high frequency performance, the noise properties of the devices are significant for their use in mixers, local oscillators or amplifiers. Extensive studies of noise in AlGaAs/GaAs HBTs have been reported, which suggest that the low frequency noise is often dominated by generation-recombination type of noise due to traps in GaAs. Measurements on InP/InGaAs HBTs have shown lower noise as compared to AlGaAs/GaAs HBTs and evidence for recombination noise due to shallow traps. We present here experimental results on the frequency dependence of noise in InP/InGaAs HBTs from 0.1 Hz to 1 MHz. The purpose of this work is to identify the significant noise sources and to determine their dependence on external biasing conditions