In this thesis, GaN was grown on ZnAl2O4 to protect ZnO which is chemical and thermal unstable in GaN growth conditions. The feasibility of high quality GaN growth was discussed through the XRD investigation grown GaN. The final aim of this study is the obtaining free-standing GaN substrate which is free from the problems such as crack, bending, and complexity. If the high quality free-standing GaN substrate is achieved, the problems such as bending and dislocations can be resolved from the heteroepitaxy that is caused by lattice mismatch and difference of thermal expansion coefficient.
In the chapter 1, the fundamental GaN properties, applications, problems in the GaN heteroepitaxy, inportance of free-standing GaN substrate, and purpose of this thesis are introduced. In the chapter 2, the growth steps and principles of measurement are explained. In the chapter 3, the investigation about ZnO growth is treated. The structural properties of ZnO films at optimized conditions are studied. In the chapter 4, the optimization of the solid phase reaction was studied to form ZnAl2O4. In the chapter 5, the effect of ZnAl2O4 was confirmed by HVPE GaN growth. The reduction of Zn out-diffusion was appeared from the measurement results. It shows us the fact that ZnAl2O4 spinel layer is helpful for the reduction of zinc and oxygen diffusion into GaN during the HVPE growth. Finally, the results found from this thesis are summarized and concluded in the chapter 6.