DEFECTS IN AMORPHOUS CHALCOGENIDES AND SILICON

Abstract
Our comprehension of the physical properties of amorphous semiconductors has improved considerably over the past few years, but many puzzles remain. From our present perspective, the major features of chalcogenide glasses appear to be well understood, and some of the fine points which have arisen recently have been explained within the same general model. On the other hand, there are a grear number of unresolved mysteries with regard to amorphous silicon-based alloys. In this paper, the valence-alternation model for chalcogenide glasses is briefly reviewed. Two recent problems, the observations of dispersive transport in arsenic selenide glasses and of large transient field field effects in arsenic telluride glasses are analyzed in detail. The present status of the analogous defect model for amorphous silicon alloys is discussed. Some of the major puzzles, the Staebler-Wronski effect, the Meyer-Neldel rule, and the mechanism for doping, are examined.