Band structures, gap states and doping effects in amorphous hydrogenated and crystalline silicon studied by soft X-ray emission

The soft X-ray L₂₃ emission spectra for various hydrogenated amorphous silicon (ASIL) and crystalline silicon samples have been analysed. The significant differences in the valence band structure for p-type compared with n- and i-type ASIL films are ascribed to greater structural disorder in the former. The presence of apparent high densities of states in the ASIL energy gap region is ascribed to cross transitions from nearest-neighbour hydrogen states to shifted core states of silicon. Both B and P dopant atoms have been directly detected from their emission spectra. Comparison of results for ASIL films made with 1% and 20% phosphine-in-silane show a gas atom incorporation ratio that is seven times higher for the 20% film.