Epitaxial growth of α-Ga2O3 thin films on a-, m-, and r-plane sapphire substrates by mist chemical vapor deposition using α-Fe2O3 buffer layers

Epitaxial a-, m-, and r-plane α-Ga2O3 thin films were successfully grown on a-, m-, and r-plane sapphire substrates through the insertion of α-Fe2O3 buffer layers using mist chemical vapor deposition. The α-Fe2O3 buffer layers improved the crystal growth of the α-Ga2O3 thin films. We reveal that the out-of-plane and in-plane orientations of each plane α-Ga2O3 thin film corresponded to that of each plane sapphire substrate. The direct bandgap of the α-Ga2O3 thin films from the optical transmittance and reflectance results of a-, m-, and r-planes was estimated to be 5.15-5.2 eV. The epitaxial α-Ga2O3 thin films on the various sapphire substrates are promising materials for power devices and deep ultraviolet region optoelectronic devices.