In this study, we report the effect of pre-treatment of alpha-Ga2O3 grown on a sapphire substrate by halide vapor phase epitaxy (HVPE). During the pre-treatment process, 10 sccm of GaCl gas was injected to the sapphire substrate at 470℃. The surface morphologies of the alpha-Ga2O3 layers grown with various pre-treatment time (3, 5, and 10 min) were flat and crack-free. The transmittance of the alpha-Ga2O3 epi-layers was measured to analyze their optical properties. The transmittance was over 80% within the range of visible light. The strain in the alpha-Ga2O3 grown with a pre-treat 5 min was measured, and was found to be close to the theoretical XRD peak position. This can be explained by the reduction of strain having caused a lattice mismatch between the alpha-Ga2O3 layer and sapphire substrate. The calculated dislocation density of the screw and edge were 2.5×105 cm-2 and 8.8×109 cm-2, respectively.
