Observation of light-induced defect formation in hydrogenated amorphous silicon by subgap illumination

The effect of subgap illumination on the formation of light-induced defects in hydrogenated amorphous silicon was investigated using photothermal deflection spectroscopy. As with broadband illumination, an enhancement in the subgap absorption is observed and is related to the silicon dangling bonds. The magnitude of the enhancement varies with the photon energy and with the amount of doping. The results are consistent with the mechanism of recombination of photoexcited electrons with trapped holes producing metastable defects.