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

Abstract

We conduct a systematic investigation of the valence band offset ΔEv for amorphous/crystalline silicon heterojunctions (a-Si:H/c-Si) using low-energy photoelectron spectroscopy in the constant final state mode. The dependence of ΔEv 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. ΔEv is found to be independent of both substrate and film doping and amounts to ΔEv¯=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 ΔEv 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.