Origin of lateral photovoltage in hydrogenated amorphous silicon and silicon germanium thin films

Large lateral photovoltages (LPVs) have been measured in hydrogenated amorphous silicon and silicon germanium thin films. We find that LPV increases upon light soaking (LS) the samples. The diffusion lengths of photocarriers have been measured by the steady state photocarrier grating (SSPG) technique in annealed and light soaked states. Our study shows that the knowledge of carrier diffusion lengths and photoconductivity is not sufficient in understanding LPV and that it can be explained in terms of potential fluctuations present in the sample.