Role of interfacial compound formation associated with the use of ZnO buffers layers in the hydride vapor phase epitaxy of GaN

ZnO buffer layers have been used in the hydride vapor phase epitaxy of GaN in order to improve the initial nucleation and growth of the GaN and hence the subsequent materials properties. The specific role of the ZnO buffer layer was investigated by x-ray photoelectron spectroscopy and x-ray diffraction. The improvements in the GaN growth behavior are attributed to the formation of a thin surface layer of ZnAl2O4 that results from a reaction-diffusion process between the ZnO and Al2O3. This layer can provide an improved lattice match to GaN as well as change in surface energy affecting the initial growth of the GaN.