Structures and stability of GaN/Ga2O3 interfaces: a first-principles study

The structures and stability of the interface between GaN and Ga2O3 are theoretically investigated on the basis of first-principles calculations. We determine the stable structures of the interfaces with alpha-phase and beta-phase Ga2O3 (GaN/alpha-Ga2O3 and GaN/beta-Ga2O3 interfaces, respectively) using absolute interface energies. The calculated absolute interface energies for various atomic configurations demonstrate that the stable structure strongly depends on the oxygen chemical potential. For the GaN/alpha-Ga2O3 interface, the structures with Ga vacancy are stabilized over the wide range of oxygen chemical potential. On the other hand, the interface with Ga-O bonds are favorable over the wide range of oxygen chemical potential for the GaN/beta-Ga2O3 interface. Furthermore, we clarify the interface structures of GaN/Ga2O3 by considering the experimental thermal oxidation conditions. The calculated results provide firm theoretical frameworks to understand the formation mechanism of oxide films by thermal oxidation of GaN substrate.