Effects of base geometry on volume recombination transistor base and on transistor gain factor

Abstract

An eloctrolytic tank model of a transistor base is used to directly simulate volume recombination in tho base. The relative magnitudes of tho base current components due to (1) volume recombination in the axial region of tho base, (2) volume recombination in the transverse region of the base, (3) direct minority carrier transverse flow into the base contact and (4) surfaces recombination in the base are found for various combinations of base geometry, base lifetime, and surface recombination velocity. Surface recombination current is shown to bo relatively less important compared to the rest except when surface conditions ore very poor. Even when the surface is poor, the other components are found to be comparable. The latter three components are all affectted by base geometry in the same manner so that dependence of transistor current gain factor on base geometry which has been previously attributed to the effects of surface recombination may need reconsideration. The gain bandwidth product of the transi...