Base transit time of an epitaxial n~+pn~-n~+ bipolar transistor considering Kirk effect

摘要

First an analytical expression for the base transit time in an epitaxial n~+pn~-n~+ bipolar transistor considering the field-dependent mobility and the electron velocity saturation before the onset of the Kirk effect is obtained. The base transit time is found to increase at the high collector current density. Whereas the existing analytical models show decrease of the transit time with the increase of the collector current density. The base transit time with the Kirk effect is also studied with a simple equation for transit time obtained after modifying De Graaff-Kloosterman formula for collector current. The Kirk effect is found to influence the base transit time of a bipolar transistor with highly doped base significantly at large collector current density.