In this study, a nano-columnar low-temperature (LT) GaN buffer was used to reduce the wafer bowing of a GaN layer grown on a sapphire substrate. A significant reduction in the extent of wafer bowing was observed for the GaN layer for the preserved nano-columnar LT GaN layer when compared with the conventional GaN layer. These results suggest that the preserved nano-columnar structure helped relax the GaN layer strain energy associated with thermal expansion mismatch. The flow of TMGa during the temperature ramp-up from LT to high-temperature was found to be an important process parameter to preserving the nano-columnar structure of LT GaN, resulting in less bowed GaN on sapphire. (C) 2013 Elsevier B.V. All rights reserved.