GaN epilayers and AlGaN/GaN superlattice structures have been deposited on (0001) ZnO substrates by metalorganic vapor phase epitaxy (MOVPE) using GaN and AlN buffer layers. The growth conditions were first optimized on GaN templates using N2 as carrier gas at relatively low temperature (<800 °C), which is suitable for GaN growth on a ZnO substrate. Experimental results show that high interfacial quality can be achieved in the superlattice by using TMIn as a surfactant. The optimized growth conditions were subsequently transferred to ZnO substrates. The influence of growth temperature on the material quality was studied. A proper growth temperature for both GaN cover layer and AlGaN/GaN superlattice can improve the structural and optical properties of the structures on ZnO. This improvement is verified using x-ray diffraction, atomic force microscopy and photoluminescence characterizations. The growth temperature must be chosen with these two factors in mind, with too low a growth temperature leading to poor quality material and too high a temperature causing reactions at the GaN/ZnO interface that degrade quality. AlN buffer layers on ZnO were also studied to increase subsequent GaN epilayer quality. Effects of buffer layer growth conditions on optical and structural quality were studied.