PICOSECOND SPECTROSCOPY.

Abstract

Picosecond transient grating spectroscopy is applied to research on the dynamics of excited carriers in amorphous semiconductors. Using this technique, the dynamics of the photodarkening process in As//2S//3 chalcogenide glass, as well as the carrier dynamics in optically illuminated glow discharge a-Si: H, are clarified. The observed dynamic behavior of the photodarkening process is such that excited carriers diffuse in mobile states and relax to a photodarkening state through localized states near the midgap. In optically illuminated a-Si: H, a picosecond rapid relaxation is found. This is explained by the multiple trapping mechanism, taking account of shallow and deep localized states, which increase after optical illumination.