Base Region Transport Characteristics of a Diffused Transistor

Abstract

A one-dimensional analysis is given on the minority carrier transport characteristics of a transistor base region containing an arbitrary drift field distribution. This field is assumed to enhance—or retard—the motion of minority carriers between an emitter and collector junction, thereby modifying the influence of bulk recombination mechanisms. Base region transport efficiency is established in terms of the transistor current gain when an ideal emitter junction is assumed. Applications of this analysis are demonstrated by establishing the base region transport efficiency for diffused transistors. Two types of structures have been analytically investigated: the alloy-diffused transistor, containing a diffused collector junction and an alloy-type emitter; and the double-diffused transistor constructed entirely by diffusion techniques. For practical semiconductor devices, a comparison of these two structures has shown negligible differences in their base region transport efficiency and, furthermore, the drift mechanisms within these diffused devices have little influence upon their one-dimensional current gain.