Heteroepitaxial Growth of Thick α‑Ga₂O₃ Films on Sapphire Substrates by Flow Modulation Epitaxy with Halide Vapor Phase Epitaxy

In this study, halide vapor phase epitaxy with flow modulation epitaxy (FME) was used to grow a 10 μm thick single-crystalline α-Ga₂O₃ epilayer on a sapphire substrate. By optimizing the interval time of the gas, highly crystalline thick α-Ga₂O₃ epitaxial layers can be grown without any cracks. The as-grown α-Ga₂O₃ was evaluated using scanning electron microscopy and atomic force microscopy to analyze the improvement in the surface morphology and roughness of the epitaxial layer, while X-ray diffraction was used to evaluate the crystallinity. Under optimized O₂ FME conditions, the thick α-Ga₂O₃ film exhibited a lower full width at half-maximum (fwhm) of 779 arcsec for the (101̅4) plane compared to the (101̅4) plane fwhm values of 1137 and 925 arcsec obtained for the reference and HCl FME conditions, respectively. The results indicated that the α-Ga₂O₃ epitaxial layer grown under the O₂ FME conditions exhibited the best quality. This confirms that the current approach to growing high-quality α-Ga₂O₃ thick films is stable.