A MODEL-BASED COMPARISON OF THE PERFORMANCE OF ALGAAS GAAS AND SI/SIGE HETEROJUNCTION BIPOLAR-TRANSISTORS (HBTS) INCLUDING THERMAL EFFECTS/

The performances of AlGaAs/GaAs and Si/SiGe heterojunction bipolar tra nsistors (HBTs) at room temperature are compared based on an analytica l model which includes relevant physics such as the high-current and t hermal (or self-heating) effects. Three figures of merit of the HBTs a re calculated and compared: the dc current gain, cutoff frequency, and maximum oscillation frequency. Our results indicate that the AlGaAs/G aAs HBT possesses less uniform but higher peak current gain, cutoff fr equency, and maximum oscillation frequency than its Si/SiGe counterpar t. Furthermore, at high current densities, it has been shown that the thermal effect becomes important and degrades the performance of AlGaA s/GaAs HBT more significantly than that of Si/SiGe HBT due primarily t o the poorer GaAs thermal conductivity than Si.