In-plane orientation control of (001) <i>κ</i> -Ga <sub>2</sub> O <sub>3</sub> by epitaxial lateral overgrowth through a geometrical natural selection mechanism
Yuichi Oshima, Katsuaki Kawara, Takayoshi Oshima, Takashi Shinohe
Abstract
Abstract Vapor phase growth of c -plane κ -Ga 2 O 3 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 -Ga 2 O 3 was grown by epitaxial lateral overgrowth. A SiO x mask with a striped or dotted-striped pattern was aligned on a c -plane sapphire substrate with a TiO x buffer layer so that the stripe was parallel to the [ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn mathvariant="normal">11</mml:mn> <mml:mover accent="true"> <mml:mn>2</mml:mn> <mml:mrow> <mml:mo stretchy="true">¯</mml:mo> </mml:mrow> </mml:mover> <mml:mn>0</mml:mn> </mml:math> ] direction of the sapphire. κ -Ga 2 O 3 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 -Ga 2 O 3 domains converged into one whose [010] direction was perpendicular to the stripe. The convergence occurred through a geometrical natural selection mechanism.