Two-Step Growth of (0001) ZnO Single-Crystal Layers on (0001) Sapphire Substrates by Halide Vapor Phase Epitaxy

Abstract

The heteroepitaxial growth of (0001) ZnO on (0001) sapphire substrates by halide vapor phase epitaxy using a two-step growth procedure was investigated. X-ray diffraction analysis revealed that single-crystal (0001) ZnO layers on (0001) sapphire substrates were grown at 400 °C. High-temperature heteroepitaxy at 1000 °C on (0001) sapphire substrates was realized by two-step growth using the ZnO layer grown at 400 °C as a buffer layer. Two-dimensional layer growth at 1000 °C was realized on buffer layers thicker than 0.4 µm. Photoluminescence (PL) measurements performed at room temperature for the ZnO layer grown on the 0.4-µm-thick buffer layer showed a significant blueshift of near-band-edge emission (NBE). A thick buffer layer of 0.8 µm was found to be necessary for a successful two-step growth without a blueshift of NBE in the PL spectra, which is caused by a large compressive stress.