Distribution of recombination current in emitter-base junctions of silicon transistors

Sah, Noyce and Shockley have attributed the decrease in the current gain of silicon transistors to recombination in the space-charge region of the emitter-base junction. It is suggested that for oxide-masked diffused structures the space-charge recombination current is concentrated at the junction periphery at or just under the surface. An analysis is presented which shows that measurement of the base current of transistor structures with two base contacts, as a function of voltage applied between the two base contacts, may be used to distinguish between recombination current which is concentrated at or near the surface periphery of the junction space-charge region, and recombination current distributed over the area of the junction. For the diffused structures examined, it is shown experimentally that the recombination takes place mainly at or near the junction surface periphery.