Growth and nitridation of β-Ga2O3 thin films by Sol-Gel spin-coating epitaxy with post-annealing process

β-Ga2O3 thin films have been successfully prepared on (0001) sapphire substrate by simple and effective sol-gel spin-coating method with post-annealing process (SSP). The effects of different preheating temperatures on the crystal quality and surface morphology of β-Ga2O3 films have been systematically investigated. The β-Ga2O3 thin films exhibit good crystallinity with (2¯\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar 2$$\end{document}01) preferred orientation and smooth surface morphology. The results showed that β-Ga2O3 thin films directly grown on (0001) sapphire by SSP method have comparable or better crystal quality compared with other epitaxial methods. The β-Ga2O3 thin films annealed at 1000 °C with the preheating temperature of 300 °C and above have smooth and crack-free surface morphology. The single-domain-growth mode of β-Ga2O3 thin film prepared on ~7° off-angled (0001) sapphire substrate toward <112¯\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar 2$$\end{document}0> plane has been confirmed by SSP method, and the porous GaN layers have been obtained by the nitridation of the Sol-Gel grown β-Ga2O3 thin films for future applications in high-quality free-standing GaN substrates.