DEFECTS IN AMORPHOUS-SILICON - EXTRINSIC OR INTRINSIC

Competing types of models of dangling-bond defects in hydrogenated amorphous silicon are analyzed in the light of recent advances in descriptions of light-induced defects such as saturation of their density and stretched-exponential kinetics. The familiar intrinsic models (Si-Si bond breaking) are found to have several serious problems- more than generally recognized- while extrinsic models have few. In particular, for the rehybridized two-site model based on foreign atoms, the one important need is to explain defects in undoped material.