A two-step metal organic vapor phase epitaxy growth method for high-quality ZnO on GaN/Al₂O₃ (0 0 0 1)

High-quality [0001]-oriented ZnO films were grown in a single growth experiment on GaN/Al₂O₃ applying a two-step metal organic vapor phase epitaxy growth technique. The essence of this method is the heteroepitaxy of a low-temperature ZnO buffer layer using dimethyl-zinc and tertiary-butanol precursors on GaN/Al₂O₃ and the subsequent homoepitaxial growth of a high-temperature layer using N₂O as O-precursor. The layers show smooth surface morphology and high crystalline quality as demonstrated by X-ray diffraction (FWHM of (0002) ω-scans for a 2.28μm thick layer is 160″). The bright luminescence is dominated by narrow excitonic emission lines (e.g., FWHM <1.3meV for bound exciton I ₈). Our method opens broad prospect for the growth of ZnO-based device structures.