Metal organic vapor phase epitaxy of ZnO on GaN/Si(111) using tertiary-butanol as O-precursor

High-quality ZnO was grown by metal organic vapor phase epitaxy on 1.3 mum thick GaN layers on Si(111) using dimethylzinc and tertiary-butanol as precursors. The variation of the growth temperature shows a strong correlation with the microstructure as observed by atomic force and scanning electron microscopy. With increasing growth temperature we find an increasing size of ZnO crystallites and a transition from 3D to 2D growth. Moreover, increasing the growth temperature leads to a reduction of tensile stress in the ZnO as observed by X-ray diffraction. In highly spatially resolved cathodoluminescence measurements we observe narrow (A(0),X) luminescence from the ZnO surface and a strong donator correlated luminescence at macroscopic defects.