Effects of light soaking on amorphous silicon

The effect of light soaking on a-Si:H films is well known as the Staebler-Wronski effect, though its complete mechanism is not yet clear. We studied the effect of light soaking with UV, white and sub-gap light on a-Si:H films, as well as the effect of thermal annealing in the dark. It was shown that the light soaking of the films with white and sub-bandgap light in air did not affect hydrogen concentration from Si-H bonds, and at the same time, enhanced oxidation of the films is observed. It means that oxygen incorporation was due to the broken backbonds to Si-H which very likely represent weak bonds. Moreover, it was found that, subgap and white light irradiation produced oxidation, UV light did not, while UV light caused even minor Si-H bond breaking. Vacuum annealing at 100/spl deg/C in the dark, on the other hand, caused hydrogen redistribution, enhancing Si-H bond concentration and recovering broken bonds.