Switching processes in diffused rectifiers—I theory

Abstract

The formerly developed theory for the switching of power rectifiers into the reverse state which was limited to rectifiers with abrupt pn junctions is extended to diffused structures. The following model is taken as a basis: a spatially constant basic doping by donors, into which acceptors are diffused in an exponentially decreasing distribution. The distribution of the hole concentration and the voltage drop at the side of the diffused-in doping are evaluated, both for different points in time during the switching process. The voltage increase takes place in two clearly distinguishable periods of time; first, the voltage increases exponentially with the thickness of the swept-out zone, but later on only quadratically or, if the basic doping is light, with the power 3 2 . If the basic doping is heavy, a transitory, very steep voltage increase is found between these two ranges.