Effects of self-heating and thermal-coupling on the performance of AlGaAs/GaAs heterojunction bipolar transistors

A numerical analysis is presented to investigate the effects of different base and collector structures on the dc and ac performance of AlGaAs/GaAs multi-finger heterojunction bipolar transistors (HBTs). The results show that different structures give rise to different electric fields in the base-collector junction and lattice temperatures in the HBT, which consequently affect the HBT's cutoff frequency and current gain, respectively. The physical mechanisms contributing to these differences are also discussed in detail.