Density of states and capture cross-sections in annealed and light-soaked hydrogenated amorphous silicon layers

Abstract

The density of states of a lightly p-doped hydrogenated amorphous silicon sample and the related transport behaviours were extensively studied and compared with those of intrinsic samples both in the annealed and light-soaked states. It is observed that p-doping increases the density of positively charged dangling bonds in the annealed samples, in agreement with the predictions of the defect-pool model. After light-soaking, a decrease of positively charged dangling bonds and an increase of neutral ones in the p-doped sample are observed, which is still in qualitative agreement with the predictions of the model. However, quantitatively, the results of modulated photocurrent experiments cannot be reproduced on the basis of this model. It is proposed that light-soaking either induces a variation of the defect capture cross-sections or creates a distribution of states in the gap for which the defect-pool model does not account.