Plasma-free dry etching of (001) β-Ga2O3 substrates by HCl gas

In this study, we dry etched SiO2-masked (001) b-Ga2O3 substrates in HCl gas flow at a high temperature without plasma excitation. The etching was done selectively in window areas to form holes or trenches with inner sidewalls of (100) and/or {310} facets, which are the smallest surface-energy-density plane and oxygen-close-packed slip planes, respectively. In particular, (100) faceted sidewalls were flat and relatively close to the substrate surface normal. Therefore, this simple dry etching method is promising for fabricating plasma-damage-free trenches and fins used for b-Ga2O3-based power devices.