ZnO wurtzite single crystals prepared by nanorod-assisted epitaxial lateral overgrowth

We have developed a novel method to grow thick, single crystalline ZnO films for the use of supporting layers by employing nanorod-assisted epitaxial lateral overgrowth (NRELO). The NRELO ZnO films were epitaxially grown on vertically arrayed nanorods at reduced temperatures by metalorganic chemical vapor deposition. The resultant films had epitaxial structures similar to the conventional ZnO films on sapphire and relatively low dislocation density. During the growth evolution of the NRELO films, the dominant stress was changed from nearly stress-free in the nanorods to strong in-plane tensile stress in the top region, and the rotation of the (0002) plane clearly disappeared in the NRELO ZnO film. This study shows that ZnO NRELO has the possibility to be used as supporting layers in optoelectronic devices with transparent and vertical stack structures because it exhibited high transparency, electrically semiconducting, and low defect density at the same time.