Physical compact collector-emitter breakdown model for heterojunction bipolar transistors

Collector-emitter breakdown in npn HBTs is modeled using a base-collector current equal to I-h = alpha(i)I(c), where I-c is the collector current and alpha(i) is the integral of the electron impact ionization coefficients over the base-collector depletion depth. We fit the alpha integrals for collector doping concentrations N-d similar to 0.08 to 1 x 10(17) cm(-3) to functions of the collector voltage. The model is suitable for SPICE and harmonic balance simulators, is temperature dependent, and allows voltages to be swept above the collector-emitter breakdown limit without catastrophic effects to the model convergence. (C) 1997 Elsevier Science Ltd.