Rapid growth of α -Ga 2 O 3 by HCl-boosted halide vapor phase epitaxy and effect of precursor supply conditions on crystal properties

Abstract We investigated the effect of supply conditions of GaCl, O 2 , and additional HCl on the growth rate of (0001) α -Ga 2 O 3 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 O 2 , and a rapid growth rate as high as 101 μ m h −1 was achieved. Thermodynamic analysis revealed that the addition of HCl works to convert GaCl into GaCl 3 , and it was elucidated that the parasitic gas-phase reaction was suppressed because α -Ga 2 O 3 was grown through the chemical reaction of GaCl 3 and the oxygen sources (O 2 and/or H 2 O), 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 10 1 ¯ 2 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 × 10 18 cm −3 at 101 μ m h −1 . The VI/III ratio difference did not have a significant effect on [H] or [Cl]. α -Ga 2 O 3 islands were formed through selective area growth, and the lateral/vertical growth rate ratio decreased with increasing growth rate.