Determination of band offsets at the interfaces of NiO, SiO2, Al2O3, and ITO with AlN

Abstract

The valence and conduction band offsets at the interfaces between NiO/AlN, SiO2/AlN, Al2O3/AlN, and ITO/AlN heterointerfaces were determined via x-ray photoelectron spectroscopy using the standard Kraut technique. These represent systems that potentially would be used for p-n junctions, gate dielectrics, and improved Ohmic contacts to AlN, respectively. The band alignments at NiO/AlN interfaces are nested, type-I heterojunctions with a conduction band offset of −0.38 eV and a valence band offset of −1.89 eV. The SiO2/AlN interfaces are also nested gap, type-I alignment with a conduction band offset of 1.50 eV and a valence band offset of 0.63 eV. The Al2O3/AlN interfaces are type-II (staggered) heterojunctions with a conduction band offset of −0.47 eV and a valence band offset of 0.6 eV. Finally, the ITO/AlN interfaces are type-II (staggered) heterojunctions with conduction band offsets of −2.73 eV and valence band offsets of 0.06 eV. The use of a thin layer of ITO between a metal and the AlN is a potential approach for reducing contact resistance on power electronic devices, while SiO2 is an attractive candidate for surface passivation or gate dielectric formation on AlN. Given the band alignment of the Al2O3, it would only be useful as a passivation layer. Similarly, the use of NiO as a p-type layer to AlN does not have a favorable band alignment for efficient injection of holes into the AlN.