Correlation between crystal structure and photoluminescence for epitaxial ZnO on Si(111) using a gamma-Al(2)O(3) buffer layer

Abstract

High-quality ZnO epitaxial films were grown by pulsed-laser deposition on Si (1 1 1) substrates with a thin. gamma-Al(2)O(3) buffer layer. The epitaxial. gamma-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 (1 0 0)ZnO

{2 2 (4) over bar}gamma-Al(2)O(3) or {4 (2) over bar (2) over bar}gamma- Al(2)O(3)

{2 2 (4) over bar} Si. 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 phi-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.