Influence of the distribution function shape and the band structure on impact ionization modeling

Abstract

Accurate modeling of impact ionization is a critical issue for deep submicron devices. All established analytical models for the distribution function based on the local electric field or on the local average carrier energy give rather poor results. Therefore, theoretically sound microscopic scattering rates cannot be properly transformed into accurate macroscopic models. We show that by accounting for the average square energy an accurate analytical description of the distribution function can be given. Together with a proper band structure model the analytical distribution function can then be used to evaluate microscopic models in a macroscopic device simulator. The present model is accurate for bulk and sub 100 nm feature size devices and involves only local quantities, which makes it a good choice for inclusion in conventional device simulators.