Post-transit-time analysis of time-of-flight photocurrents

Abstract

It is shown how the density of localized gap states in amorphous semiconductors can be deduced from time-of-flight photocurrents on the basis of the trap-limited band transport model, post-transit currents giving information on deep-state densities; and how strong deep-trapping of the photo-induced excess carriers invalidates the analysis. Results from a-Si:H, p-type a-Si:H, a-Si,S:H and a-Si,C:H samples are used to illustrate these points.