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 crysta l part of the emitter of a polysilicon emitter bipolar transistor is d erived. The solution is based on an existing comprehensive model which takes into account the interfacial oxide and an arbitrary number of g rains in the polysilicon layer. The emitter charge partition in polysi licon and single crystal emitter components is summarized in contour p lots for constant values of the ratio.