Stress control in ZnO films on GaN/Al2O3 via wet oxidation of Zn under various temperatures

► Epitaxial ZnO thin films were synthesized, using the wet oxidation process. ► High quality of synthesized ZnO films were obtained by applying two temperatures (420 and 470 °C). ► ·The lattice constant of ZnO films shrinked by increasing oxidation temperature through increase of oxygen diffusion in ZnO lattice. ► ·It is possible to grow controllable stress of ZnO on GaN substrate using simple method for high quality thin films.