Modeling of self-heating in GaAs/AlGaAs HBTs for accurate circuit and device analysis

An improved HBT (heterojunction bipolar transistor) large signal model has been developed which allows calculation of intrinsic device temperature as a function of the dissipated power. The time dependence of this power effect is evaluated using pulsed on-wafer measurements. The calculated temperatures are proved to be correct by diode drop measurements with a pair of standard transistors. Simplified numerical simulations of the three-dimensional heat equations give similar results. An additional test structure-a broadband amplifier with a Darlington connected pair of transistors-is simulated to predict the intrinsic device temperatures and show reliability under normal operating conditions. Their thermal behaviors are confirmed with liquid crystal measurement techniques.<>