We report the metalorganic chemical vapor deposition growth of site-controlled single GaN quantum dots (QDs) in nanowires. The structure design has been optimized to maximize the luminescence intensity. First we have investigated the effect of the growth template on the sapphire (0 0 0 1) substrate. It is found that even when the nanowire growth is performed on high defect density AlN, no degradation of the QD emission is observed (when compared to those dots grown on thick, higher quality GaN templates). As a consequence, the signal-to-noise ratio of the GaN QD emission could be improved by using the AlN templates, which exhibit a less intense background emission. Additionally, we have investigated the effect of the surface morphology of the underlying Al(Ga)N shell layers on the optical properties of the structures. When employing an AlGaN shell with smooth surface morphology, sharp single luminescence peaks from the QDs are clearly observed at around 4.2 eV. (c) 2012 Elsevier B.V. All rights reserved.