Midgap-state profiles in undoped amorphous-silicon-based alloys

Abstract

Midgap-state densities and profiles in undoped hydrogenated amorphous silicon (a-Si: H), silicon-germanium alloy (a-Si_1−x Ge_x: H) and silicon-carbon alloy (a-Si_1−xC_x:H) films were obtained from a heterojunction-monitored capacitance method. These midgap states were found to correspond to singly-occupied dangling bonds. The density of midgap states increases slowly with the Ge content in the film, while it increases rapidly with the C content. The peak of the midgap-state profile appears clearly in a-Si:H and a-Si_1−xGe_x:H, bit it does not appear clearly in a-Si_1−xC_x:H.