Numerical Modeling of Impact-Ionization Effects on Gate-Lag Phenomena in Gaas Mesfets

Abstract

Two-dimensional simulation of turn-on characteristics of GaAs MESFETs is performed in which surface states and impact ionization of carriers are considered. It is shown that the gate-lag (or the slow current transient) becomes weaker when including the impact ionization. This is attributed to the fact that the potential profiles along the surface is drastically changed when the surface states capture holes that are generated by impact ionization. The relation between the gate-lag and the so-called kink phenomenon is also discussed.