Thick $\alpha$-Ga$_{2}$O$_{3}$ layers on sapphire substrates grown by halide epitaxy

This paper reports on epitaxial film growth and characterization of $\alpha$-Ga$_{2}$O$_{3}$, a novel wide bandgap semiconducting material. The films were deposited by halide vapour phase epitaxy on basal plane sapphire substrates. The films were from 0.5 $\mu$m to over 10 $\mu$m in thickness, the latter being the record value by now. Structural and optical properties of the specimens were studied. All specimens were structurally uniform, single phase, and had a corundum-like $R\bar3c$ structure similar to that of sapphire substrate. It was found that the full width at half maximum for the (0006) $\alpha$-Ga$_{2}$O$_{3}$ reflection varies with layer thickness and approaches 240 arcsec for the thickest layer. Both thin and thick layers were transparent in the visible and UV spectral range up to the absorption edge at 5.2 eV.