Valence band offset in heterojunctions between crystalline silicon and amorphous silicon (sub)oxides (a-SiO_x:H, 0 ＜ x ＜ 2)

摘要

The heterojunction between amorphous silicon (sub)oxides (a-SiO_x:H, 0 ＜ x ＜ 2) and crystalline silicon (c-Si) is investigated. We combine chemical vapor deposition with in-system photoelectron spectroscopy in order to determine the valence band offset ΔE_Ⅴ and the interface defect density, being technologically important junction parameters. ΔE_V increases from ≈0.3eV for the a-Si:H/c-Si interface to ＞4eV for the a-SiO_2/c-Si interface, while the electronic quality of the heterointerface deteriorates. High-bandgap a-SiO_x:H is therefore unsuitable for the hole contact in heterojunction solar cells, due to electronic transport hindrance resulting from the large ΔE_V. Our method is readily applicable to other heterojunctions.