Abstract
High-quality ZnO epitaxial films were grown by pulsed-laser deposition on Si (1 1 1) substrates with a thin γ-Al 2 O 3 buffer layer. The epitaxial γ-Al 2 O 3 buffer layer consists of two (1 1 1) oriented domains rotated 60° from each other against the surface normal, which yields the in-plane epitaxial relationship or . The crystalline quality and optical properties of ZnO epi-layers were studied by x-ray diffraction and photoluminescence measurements. A clear correlation between ZnO deep-level emission (DLE) to near-band edge (NBE) emission intensity ratio and the width of the -scan across off-normal reflection was observed. The NBE linewidth also exhibits strong dependence on the width of the ZnO (0 0 2) rocking curve. These observations indicate the NBE and DLE emissions are mainly affected by the edge and screw type dislocations, respectively. © 2008 IOP Publishing Ltd.