Reversible photo-induced structural change in hydrogenated amorphous silicon

A reversible photo-induced change has been observed in the polarization dependence of a transverse electro-absorption signal for hydrogenated amorphous silicon, which is indicative of the occurrence of structural change in the whole material. The change proceeds rapidly under steady light exposure until saturation is reached, while the decrease in the photoconductivity becomes significant just after saturation. These observations convince us that a large-scale photostructural change is involved in the photo-induced degradation of the electronic properties of the material in addition to the creation of metastable dangling bond defects.