An accurate, large signal, high frequency model for GaAs HBTs

Abstract

An accurate compact circuit simulation model has been developed for the large-signal, high-frequency behavior of GaAs single heterojunction bipolar transistors (HBTs). A unified, physically-based, quasistatic collector charge function models both base-collector capacitance and collector transit time. It naturally handles collector space-charge effects, "full-depletion" of the collector n region, and the dependence of the high-field electron velocity in GaAs on electric field and temperature. An improved charge expression accounts for the Kirk effect. This formulation has produced excellent model fits to measurements of AlGaAs-GaAs HBTs.