Heteroeptaxial growth of semipolar GaN on (10 (1) over bar0) sapphire by metal-organic vapor phase epitaxy has been investigated using high temperature nucleation layers in order to provide large GaN templates for semipolar light emitters. The nitridation layer and nucleation conditions were optimized for phase pure {11 (2) over bar2} layer orientation, minimum surface roughness and improved crystal quality. Single phase {11 (2) over bar2} GaN layers were obtained by controlling the nitridation conditions and thus nitridation layer thickness. The crystal quality was improved by high temperature growth. Basal plane stacking faults were identified as the dominating defects by transmission electron microscopy. Photoluminescence measurements revealed that these defects are type I(1). A layer roughness of 4 nm was measured by atomic force microscopy. (C) 2011 Elsevier B.V. All rights reserved.