Spontaneous-polarization-induced heterojunction asymmetry in III-nitride semiconductors

Abstract

We report on precise control of film crystal polarity in fully relaxed, thin InN/AlN heterojunctions grown on sapphire by plasma-assisted molecular beam epitaxy. Using these samples, we have measured asymmetric valence band offset values (0.8 ± 0.1 eV for the In/Al− and 1.8 ± 0.1 eV for the N-polar case) at polar InN/AlN heterojuncitons by synchrotron soft x-ray photoelectron spectroscopy. We confirm that the discontinuities of spontaneous polarizations at polar InN/AlN heterointerfaces lead to the large core level shift of the Al 2p peak related to the In 4d peak (1.0 eV).