Potential Fluctuations in Intrinsic Hydrogenated Amorphous Silicon

The dangling bonds in hydrogenated amorphous silicon (a-Si:H) that can be thermally generated or light-induced result in charged defects. Inhomogeneities of a random distribution of charged defects may lead to the formation of long-range potential fluctuations which would influence the charge transport in amorphous semiconductors and limit solar cell performance. By employng the technique ofphotoconductive frequency mixing, the drift mobility (.mu.d) and photomixing lifetime (.tau.) were determined separately. Strong evidence for the existence of long-range potential fluctuations in intrinsic a-Si:H has been found from the measurements of drift mobility in light induced degradation, as a function of applied electric field and as a function of illumination light intensity.