Measurement of ZnO/Al₂O₃ Heterojunction Band Offsets by in situ X-Ray Photoelectron Spectroscopy

ZnO films are grown on c-sapphire substrates by laser molecular beam epitaxy. The band offsets of the ZnO/Al₂O₃ heterojunction are studied by in situ x-ray photoelectron spectroscopy. The valence band of Al₂O₃ is found to be 3.59±0.05 eV below that of ZnO. Together with the resulting conduction band offset of 2.04±0.05 eV, this indicates that a type-I staggered band line exists at the ZnO/Al₂O₃ heterojunction.