Experimental determination of the stored charge and effective lifetime in the emitter of junction transistors

A method is described and illustrated that enables for the first time the experimental determination of the effective lifetime τEand the excess minority-carrier charge QEin the emitter region of junction transistors. The method involves only straightforward electrical measurements made at the transistor terminals. But it requires that the analysis of the resulting data be based rigorously on the physics underlying the static and dynamic response of transistors. A brief discussion is devoted to uses of experimentally determined values of τEand QE. They can be used to study energy-gap shrinkage and recombination mechanisms in the emitter and their relation to common-emitter current gain.