Modeling of light-induced defect creation in hydrogenated amorphous silicon

Abstract

Light-induced defect creation in hydrogenated amorphous silicon $(a\text{\ensuremath{-}}\mathrm{Si}:\mathrm{H})$ is discussed in terms of a model based on the breaking of weak Si--Si bonds by self-trapping of holes under illumination. In this model, two separate dangling bonds, i.e., a normal dangling bond and a hydrogen-related dangling bond that is a dangling bond having hydrogen at a nearby site, are created under illumination. Further, we take into account dissociation of hydrogen atoms from hydrogen-related dangling bonds, termination of two types of dangling bonds by dissociated hydrogen atoms (metastable hydrogen atoms), insertion of dissociated hydrogen atoms into nearby weak Si--Si bonds, and formation of hydrogen molecules by collision of dissociated hydrogen atoms. Taking into account these processes, rate equations governing the kinetics of two types of dangling bonds and metastable hydrogen atoms under illumination are numerically solved for the case of continuous illumination. The calculated results are compared with experimental results taken from literature. Furthermore, we discuss the case of low-temperature illumination, the kinetics of light-induced dangling bonds given by stretched exponential function, and saturated density of light-induced dangling bonds in $a\text{\ensuremath{-}}\mathrm{Si}:\mathrm{H}$.