Non-polar a-plane ZnO films grown on r-Al2O3 substrates using GaN buffer layers

•GaN buffer layer has been used to grow non-polar a-plane ZnO films.•The GaN buffer thickness effect on the properties of a-plane ZnO is investigated.•GaN buffer is suitable to grow high-quality a-plane ZnO with appropriate thickness.

In this work, GaN buffer layer has been used to grow non-polar a-plane ZnO films by laser-assisted and plasma-assisted molecular beam epitaxy. The thickness of GaN buffer layer ranges from ∼3 to 12 nm. The GaN buffer thickness effect on the properties of a-plane ZnO thin films is carefully investigated. The results show that the surface morphology, crystal quality and optical properties of a-plane ZnO films are strongly correlated with the thickness of GaN buffer layer. It was found that with 6 nm GaN buffer layer, a-plane ZnO films display the best crystal quality with X-ray diffraction rocking curve full-width at half-maximum of only 161 arcsec for the (101) reflection.