Epitaxial lateral overgrowth of ε-Ga2O3 by metal-organic chemical vapor deposition

Orthorhombic epsilon-Ga2O3 is the second most stable phase of the Ga2O3 family, which is usually grown on hexagonal substrates by hetero-epitaxy. Due to the mismatch of rotational symmetry between the epsilon-Ga2O3 film and the substrate, the hetero-epitaxy of epsilon-Ga2O3 is accompanied by the problem of rotation domains, which brings a high density of defects in the film. This paper focuses on the epitaxial lateral overgrowth (ELO) of epsilon-Ga2O3 by metal-organic chemical vapor deposition (MOCVD). Based on the investigation of nucleation temperature, mask period and direction, the optimal conditions for the ELO growth of epsilon-Ga2O3 via MOCVD are established. It is found that both the thermal diffusion capability of Ga adatoms and the growth rate anisotropy of epsilon-Ga2O3 play important roles during the ELO of epsilon-Ga2O3. A high growth temperature and a short mask period can suppress the nucleation of irregular epsilon-Ga2O3 grains and improve the crystal quality. Further comparison of different designs of ELO masks revealed that the striped ELO masks predominantly promote the quasi-single-domain growth of epsilon-Ga2O3. Notably, for samples with striped ELO windows along the sapphire 112<overline>0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\left\langle {11\overline{2}0} \right\rangle$$\end{document}, rotation domains are effectively suppressed and the ratio of 0 degrees, + 120 degrees, and - 120 degrees domains increases from 1.01:1:1 to 2.6:1:1.