Breakdown voltages of base-collector junctions of high-voltage power transistors with graded collectors

Abstract

Recent work on current-mode second breakdown shows that a substantial measure of protection against failure by avalanche injections can be built into a transitistor by grading the impurity concentrations of the collector. The breakdown voltage of the base-collector junction is an important parameter for power transistors. In this paper, the open-emitter breakdown voltage of an epitaxial bipolar high-power transistor with graded collector is computed numerically. A general expression for breakdown voltage as a function of initial collector doping (doping at the collector side of the base-collector interface) and collector parameters as a function of open-base bulk breakdown voltage and current gain are also derived.