We report on the reduction of defect densities in non-polar a-plane GaN films over r-plane sapphire achieved by epitaxial laterally overgrowth (ELOG) approach. A mask pattern was used to produce ELOG GaN with wing region width of about 30μm. Based on transmission electron microscopy (TEM) results, the window regions have stacking faults density of ∼106cm -1 and threading dislocation density of ∼1010cm -2. Both ELOG Ga-face and N-face wing regions have stacking fault density of ∼105 cm-1, and dislocation density less than 108 cm-2. Cathodoluminescence studies reveal the difference in defect densities between N-faced and Ga-faced wings. GaN-based UV light-emitting diode formed on Ga-faced wing shows stronger quantum well emission and weaker parasitic emission than that formed on N-faced wing. © 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.