Halide vapor phase epitaxy of twin-free α-Ga2O3on sapphire (0001) substrates

The halide vapor phase epitaxy of α-Ga2O3 is demonstrated for the first time. The films are twin-free and heteroepitaxially grown on sapphire (0001) substrates using gallium chloride and oxygen as precursors. X-ray ω–2θ and pole figure measurements reveal that the film is single-crystalline (0001) α-Ga2O3 with no detectable formation of β-Ga2O3. The optical bandgap is determined to be 5.16 eV based on the transmittance spectrum. The growth rate monotonically increases with the partial pressures of the raw material gases, reaching approximately 150 µm/h, which is over two orders of magnitude larger than those of conventional vapor phase epitaxial growth techniques, such as mist CVD or MBE.