Physically based analytical modeling of base-collector charge, capacitance and transit time of III-V HBT´s

We present two complementary, analytical calculations of the electric field, stored charge, capacitance and transit time of the collector of a III-V HBT, for respectively low- and high bias regimes. Voltage, current and temperature dependence of base-collector capacitance as well as f_T-peaking at high bias is thus quantitatively related to GaAs-like electron drift-velocity characteristics. The physical insight developed serves as a basis for extension of the Mextram compact bipolar transistor model for circuit simulation.