Transient photoconductivity and photo-induced optical absorption in amorphous semiconductors

Abstract

Abstract Amorphous semiconductors and insulators display the phenomenon of dispersive transport: the average mobility of the carriers decreases with time after pulsed excitation. A simple model explains how multiple trapping (MT) in a continuous distribution of localized states gives rise to dispersion. This model is then used to show what can be learned about the material from a complete study of its dispersive transport when MT is known to be the origin of the dispersion. Transient photo-induced optical absorption (PA) provides a direct test of the presence of the MT mechanism. Transient photocurrent (PC) then provides the spectrum of the localized states when examined in the time regime before recombination begins. Using this density of states, many of the parameters that characterize transport and recombination, both monomolecular (MR) and bimolecular (BR), can be determined. The assumption that thermal excitation from localized states to higher-energy transport states limits both thermalization and r...