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 µm 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 (A0,X) luminescence from the ZnO surface and a strong donator correlated luminescence at macroscopic defects.