Identification of defects in amorphous silicon

Defects in amorphous Si:H are identified by a new atomic model encompassing built-in defects and light-induced defects. The model consists of a metastable localized center having an atom with two possible sites, as in the Chadi and Chang model for DX centers in crystalline GaAs. Specific rehybridizations for two-site atoms produce changes in charge state and bonding that explain a wide range of effects, including n-type or p-type doping or compensation, the Staebler-Wronski effect and its variations with doping, quench-induced defects, and defect spin.