Effect of an Al-adlayer in the c-plane ZnO/AlN heterostructure

Abstract

The stability and band offsets of ZnO on c-plane AlN substrates with and without an Al-adlayer are studied by first-principles calculations. We determine the ZnO/AlN heterostructure by a layer-by-layer mode from the initial adsorption of the alternative layers of Zn and oxygen atoms of the first ZnO unit cell on c-plane AlN surfaces. The Al-adlayer occupies the top sites of AlN substrates and improves the ordered structure of the grown ZnO. The atomic charges, electronic density of states, and band alignment are systematically analyzed for the optimized ZnO/AlN heterojunction. The Al-adlayer induces in-gap states and causes the decrease of the band offsets for the Zn-terminated ZnO/AlN () heterojunction.