Epitaxial growth of nonpolar ZnO by MOVPE

Epitaxial growth characteristics of nonpolar (M‐ and A‐plane) ZnO on M‐ and R‐plane sapphire substrates were investigated. The growth of ZnO along the c‐axis direction, which aligns parallel to [2‐1‐10] and [01‐11] directions of M‐ and R‐plane sapphire, is achieved under lower growth temperature and/or VI/II ratio, and this growth direction is preferable for smooth lateral growth. Increasing the growth time, the surface becomes rough on M‐plane, while is significantly improved on R‐plane sapphire. The growth behaviour on R‐plane sapphire can be attributed to the small lattice mismatching along the ZnO c‐axis direction and enhanced lateral growth characteristics. From photoluminescence measurements, the appearance of peak at 3.383 eV, which is at higher energy compared to well‐known impurity‐ and/or defect‐related peaks, at 10 K suggests the residual strain in ZnO films. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)