Structural stability and band alignment in the c-plane ZnO/GaN heterostructure

Abstract

The structural stability and electronic properties of ZnO on c-plane GaN substrates with and without a Ga-adlayer or Ga-bilayer are studied by first-principles calculations. The ZnO/GaN heterostructures are determined by a layer-by-layer mode from the initial adsorption of the alternative Zn and oxygen atomic layers of the first ZnO unit cell on c-plane GaN surfaces. The Ga-adlayer occupies the T4 sites of GaN (0001) substrates and improves the ordered structure of the grown ZnO. The atomic and the electronic structures are systematically analyzed for the optimized ZnO/GaN heterojunction. The perfect Zn-terminated ZnO/GaN (000) heterostructure has a band gap 2.57 eV and small band offset values, which is a potential candidate for GaN-based semiconductor heterojunction field-effect transistors devices. The Ga-adlayer induces in-gap states and causes a decrease of the band offsets for the Zn-terminated ZnO/GaN (000) heterojunction.