The Effect of Extrinsic Base Encroachment on the Switch-On Transient of Advanced Narrow-Emitter Bipolar Transistors

Abstract

This paper presents a detailed two-dimensional numerical simulation study on the switch-on transient of advanced narrow-emitter bipolar transistors. Particular emphasis is placed on the effect of the “link-up” region between the extrinsic and intrinsic bases. It is shown that, due to the nonuniform current distribution during the switch-on transient, the encroachment of the extrinsic base into the intrinsic base area causes much more severe degradation in the switching speed of the device than those predicted by dc or quasi-static ac analyses. The design considerations and scaling implications imposed by this transient phenomenon are presented. © 1988 IEEE