Growth of thick GaN layer on ZnAl2O4 spinel layer by HVPE

Thick GaN film was grown by hydride vapor phase epitaxy (HVPE) on spinel covered ZnO layer. Single crystal ZnO was grown on c-plane sapphire by ultra high vacuum (UHV) DC sputtering. A thin Al layer was thermally deposited on it. A spinel layer was formed by a solid phase reaction of the Al and ZnO layers, and GaN thick film was grown on it. Structural and chemical properties of the spinel layer were studied by X-ray diffraction (XRD) and secondary ion mass spectroscopy (SIMS), respectively. The crystal quality of GaN was observed by atomic force microscope (AFM) and transmission electron microscope (TEM). We found that the spinel layer is helpful for the reduction of zinc and oxygen diffusion into GaN during the HVPE growth. ► Single crystal ZnO was grown on c-plane sapphire by ultra high vacuum sputter. ► ZnAl2O4 spinel layer was formed by solid phase reaction which is simple and easy. ► It was confirmed that ZnAl2O4 is useful to reduce the out diffusion of ZnO during the GaN growth. ► In contrast to the GaN/ZnO, GaN/ZnAl2O4 specimen showed dominant band-edge emission in photoluminescence spectra.