Potential fluctuations and metastabilities in hydrogenated amorphous silicon

Abstract

The inhomogeneities present in hydrogenated amorphous silicon (a-Si : H) give rise to potential fluctuations. They influence the electronic properties of a-Si : H in a profound manner. Nevertheless, very few theoretical and experimental studies acknowledge their presence, because of the inherent difficulties in dealing with them. We find that the width of the potential fluctuations obtained from transport measurements is much smaller than that obtained by optical methods. This may be because the former (transport) depends on long-range potential fluctuations, whereas the latter is sensitive to short-range ones. External perturbations, e.g. light soaking and thermal quenching, are found to have different effects on the long-range potential fluctuations. Light soaking (the Staebler–Wronski effect) seems to increase them, whereas thermal quenching leaves them unchanged.