Effects of High Electric Fields and Temperature on Conductivity of a-Si

Abstract

At high electric fields the Poole-Frenkel effect and thermally-assisted tunneling give rise to an enhanced electric conductivity of amorphous silicon (a-Si). The occupancy of states in the gap, free, and trapped charge carrier concentrations and electric conductivity of a homogenous a-Si in steady-state conditions are calculated on the basis of space-charge neutrality and with time-unchangeable concentrations of charge carriers. Simplifying approximations are introduced, thus enabling easier calculations of carrier concentrations and conductivity. The theory of capture-emission dynamics in a-Si at high fields is further extended by expressing occupancy functions and nonequilibrium quasi-Fermi levels. Effects of the density of states distribution in a-Si and added impurities upon carrier concentrations and conductivity are revealed.