GaN Nanorods and Nanotubes 35 Epitaxial Growth of ZnO-GaN Hetero-Nanorods and GaN Nanotubes

Various methods to grow high quality and perfectly arranged ZnO nanorods have been reported over the recent years (see, e.g., [1, 2] and references therein). However, due to the material properties of ZnO and its related compounds, there are many restrictions in designing more complex heterostructures or even devices based on such nanorods. In particular p-type doping of ZnO is still a big, yet unsolved challenge. On the other hand, GaN and its related compounds, having similar band gap and lattice constant as ZnO, have been successfully used for the realization of a huge number of various devices owing to the fact that many issues related to heterostructures and to nand p-type doping could be successfully solved. However, for this material class, the deposition of ordered low-dimensional structures like nanorods is very difficult, typically leading only to a very disordered growth of nanowires in contrast to the above mentioned highly ordered ZnO nanorod structures. Therefore, we have investigated the combination of these two material approaches by growing GaN epitaxially around ZnO nanorods. Similar studies have been reported by An et al. [3].