In-plane orientation control of (001) κ-Ga2O3 by epitaxial lateral overgrowth through a geometrical natural selection mechanism

Abstract

Vapor phase growth of c-plane κ-Ga2O3 films has been reported on various substrates such as sapphire, GaN, and AlN. However, these films are not single crystalline, but rather a mixture of nanometer-sized in-plane 120° rotational domains. We demonstrate a technique that solves the in-plane rotational domain problem. κ-Ga2O3 was grown by epitaxial lateral overgrowth. A SiOx mask with a striped or dotted-striped pattern was aligned on a c-plane sapphire substrate with a TiOx buffer layer so that the stripe was parallel to the [] direction of the sapphire. κ-Ga2O3 was then grown on the substrate by halide vapor phase epitaxy. Electron backscatter diffraction, X-ray diffraction, transmission electron microscopy, and selective area electron diffraction revealed that the three in-plane orientations of the κ-Ga2O3 domains converged into one whose [010] direction was perpendicular to the stripe. The convergence occurred through a geometrical natural selection mechanism.