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

•α-Ga2O3 thin films grown on sapphire substrates by inserting α-Fe2O3 buffer layers.•α-Fe2O3 buffer layers improve crystal growth of all the α-Ga2O3 thin film planes.•A direct bandgap of 5.15–5.2eV for the α-Ga2O3 thin films was estimated. 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 5.15–5.2eV. The epitaxial α-Ga2O3 thin films on the various sapphire substrates are promising materials for power devices and deep ultraviolet region optoelectronic devices.