Photo-induced structural and physico-chemical changes in amorphous chalcogenide semiconductors

The various photo-induced phenomena that occur in chalcogenide glasses are classified and described, with particular emphasis on the photo-dissolution effect. The detailed mechanisms responsible for many of these processes are still unknown, although in the case of photo-darkening in annealed a-As2S3 films, Raman experiments indicate that a light-induced change in the bond distribution from that for a chemically-ordered network towards one characteristic of a random network may be the principal cause. New results on the photo-dissolution of silver into As-S films are presented which indicate that the actinic radiation initiating the effect is absorbed in the photo-doped layer, close to the interface with the undoped region of the chalcogenide film. The basic mechanism responsible for the effect, however, is still not known.