MOCVD Growth of ZnO for Optoelectronic Applications

In this paper we report on the metal-organic chemical vapour deposition of ZnO layers. We focus on heteroepitaxial growth on c-plane Al2O3 and the influence of the VI/II ratio during growth on the properties of the layers. The layer quality has been investigated by HRXRD, PL and reflectivity measurements. Under optimized growth conditions the photoluminescence is dominated by strong near band edge emission lines with half widths below 4 meV and the excitonic signals are clearly visible in reflectivity measurements. Hall effect measurements indicate an n-type background doping in the 1017 cm—3 range, and mobilities of more than 100 cm2/Vs can be reached. Moreover, a post-growth annealing step is found to improve the quality of the layers grown under suboptimal conditions. The problem of strain will be addressed and a tensile strain can be confirmed in the heteroepitaxial ZnO layers.