Impact ionization coefficient and energy distribution function in polar and nonpolar semiconductors

Abstract

An approximate solution of the Boltzmann transport equation is used to arrive at an expression for the electron energy distribution function. All major scattering mechanisms, including intervalley scattering, are included, and a distinction is made between nonpolar (Si, Ge) and polar (GaAs) optical phonon scattering. Numerically calculated impact ionization coefficients for electrons and holes in Ge, Si, and GaAs compare favorably with almost all experimental results reported in the literature. In polar semiconductors, in particular GaAs, intervalley scattering is found to dominate.