Hydrogenated amorphous silicon (a-Si:H) and hydrogenated amorphous silicon-oxide alloy films (a-SiOx:H) were investigated by temperature dependence of lateral photovoltage (LPV) measurements. The suboxide sample with  = 27 at.%, was found to exhibit larger LPV compared to the unalloyed sample. It is difficult to simply correlate LPV measurements to related diffusion length measurements, only. On the other hand, the observed magnitude of LPV in a-Si:H and its decrease with temperature, could be explained based on an internal electric field induced by diffusion electron and hole currents, and multiple trapping of the photocarriers. (c) 2005 Elsevier B.V. All rights reserved.