Metalorganic vapor phase epitaxy of ZnO: towards p-type conductivity

The promising II-VI-semiconductor ZnO has achieved strong interest in research in the past years. Especially, epitaxial growth by metal organic vapor phase epitaxy (MOVPE) is a matter of particular interest due to the large scalability of MOVPE for commercial mass production and its proven high layer quality for other compound semiconductors. In the past years tremendous advance has been made in the field of epitaxial growth. However, due to the lack of epiready ZnO substrates, so far mostly heteroepitaxial growth with a multistep growth process was applied to obtain good surface morphology and until now not all of the physical properties of such multilayers are fully understood. In this paper we present recent results of the electrical behavior of such multiple undoped ZnO layers. Despite numerous efforts one big challenge is the p-type doping of ZnO. Here we present our results to doping experiments with arsenic, nitrogen and as a new approach simultaneous dual doping of nitrogen and arsenic. Homoepitaxial growth offers a great potential for ZnO due to some advantages as the absence of thermal and lattice mismatch and potentially low dislocation density. We present experiments on the thermal treatment of commercial ZnO bulk crystals, which is necessary for subsequent homo- MOVPE.