Doping type and thickness dependence of band offsets at the amorphous/crystalline silicon heterojunction

We conduct a systematic investigation of the valence band offset Delta E(v) for amorphous/crystalline silicon heterojunctions (a-Si:H/c-Si) using low-energy photoelectron spectroscopy in the constant final state mode. The dependence of Delta E(v) on a-Si:H thickness as well as on the possible combinations of c-Si substrate and a-Si:H film doping types are explored. Delta E(v) is found to be independent of both substrate and film doping and amounts to Delta E(v) = 0.458(6)eV, averaged over all doping combinations and thicknesses, with a systematic error of 50-60 meV. A slight but statistically significant dependency of Delta E(v) on the a-Si:H film thickness may be explained by a changing interface dipole due to variations in dangling bond saturation during a-Si:H growth. (C) 2011 American Institute of Physics. [doi:10.1063/1.3559296]