Rapid growth of α-Ga2O3 by HCl-boosted halide vapor phase epitaxy and effect of precursor supply conditions on crystal properties

We investigated the effect of supply conditions of GaCl, O2, and additional HCl on the growth rate of (0001) α-Ga2O3 by halide vapor phase epitaxy and the crystal properties. The parasitic gas-phase reaction was markedly suppressed by supplying HCl gas in addition to GaCl and O2, and a rapid growth rate as high as 101 μm h−1 was achieved. Thermodynamic analysis revealed that the addition of HCl works to convert GaCl into GaCl3, and it was elucidated that the parasitic gas-phase reaction was suppressed because α-Ga2O3 was grown through the chemical reaction of GaCl3 and the oxygen sources (O2 and/or H2O), the equilibrium constant of which is much smaller than that when GaCl is used. The full-width at half-maximum of the x-ray rocking curve of diffraction measured in skew-symmetric geometry decreased with increasing growth rate by increasing the precursor supply, whereas that of symmetric 0006 diffraction did not show a systematic tendency. H and Cl impurities were detected in the unintentionally doped epilayers by secondary ion mass spectrometry. [Cl] increased rapidly with increasing growth rate, reaching 1.4 × 1018 cm−3 at 101 μm h−1. The VI/III ratio difference did not have a significant effect on [H] or [Cl]. α-Ga2O3 islands were formed through selective area growth, and the lateral/vertical growth rate ratio decreased with increasing growth rate.