A theoretical study of light induced defect creation, annealing and photoconductivity degradation in a-Si : H

摘要

This work is a theoretical study of the defect creation and annealing, and of the photoconductivity degradation of an intrinsic a-Si:H film under continuous illumination. A new model is developed for the Staebler-Wronski effect (SWE). In this model, we consider that a defect of the SiHD type is locally created by a non-radiative recombination at a weak bond close to a SiHHSi configuration. Also, it is considered that the light induced defect (LID) annealing requires a hydrogen diffusion motion. Using the fact that the areas of defect Gaussians increase with illumination time while their positions and widths remain unchanged, we present the evolution of the gap state defect density, calculated by the defect pool model, with illumination time. This density of states, which varies during illumination, is introduced in the simulation of the photoconductivity to obtain its degradation. In addition, the validity of the proportionality of the photoconductivity to the illumination intensity G and to the inverse dangling bond density is assessed. Our investigations show a monomolecular behaviour of the photoconductivity (sigma(ph) proportional to N-d(-gamma), gamma similar to 1) for moderate intensity. They also show an illumination intensity dependency on G(alpha), with alpha varying between 0.5 and 1, in agreement with a large number of similar investigations.