A COMPACT CHARGE RATIO EXPRESSION FOR THE EMITTER DELAY OF POLYSILICON EMITTER BIPOLAR-TRANSISTORS

A compact solution for the ratio of the excess minority carrier charge stored into the polysilicon to the charge stored in the single crystal part of the emitter of a polysilicon emitter bipolar transistor is derived. The solution is based on an existing comprehensive model which takes into account the interfacial oxide and an arbitrary number of grains in the polysilicon layer. The emitter charge partition in polysilicon and single crystal emitter components is summarized in contour plots for constant values of the ratio.