Natural band alignments of InN/GaN/AlN nanorod heterojunctions

Abstract

Valence band alignments of wurtzite III-nitride semiconductor heterojunctions are investigated using cross-sectional scanning photoelectron microscopy and spectroscopy on the nonpolar side-facet of a vertically −c-axis-aligned heterostructure nanorod array. The nonpolar measurement geometry and near fully relaxed lattice structure allow for the determination of “natural” band alignments without the influence of spontaneous and piezoelectric polarization fields. The valence band offsets of InN/GaN, GaN/AlN, and InN/AlN are measured to be 0.8 ± 0.1, 0.6 ± 0.1, and 1.4 ± 0.1 eV, respectively. These results are in good agreement with previous data for heteroepitaxial films and obey the expected transitivity rule.