Valence band offset of wurtzite InN∕AlN heterojunction determined by photoelectron spectroscopy

The valence band offset (VBO) at the wurtzite-type, nitrogen-polarity InN∕AlN(0001¯) heterojunction has been determined by photoelectron spectroscopy to be 3.10±0.04eV. The heterojunction samples used for this study have an atomically abrupt 8:9 commensurate interface, at which every eight-unit cell of InN aligns exactly with every nine-unit cell of AlN. The commensurately matched InN∕AlN heterojunction system grown on Si(111) is particularly suitable for the determination of VBO since both InN and AlN epitaxial layers are completely relaxed and the strain-induced piezoelectric fields, which are difficult to be quantitatively determined, have a negligible effect.