Optically specular a-plane GaN was grown on r-sapphire substrate by metal-organic chemical vapor deposition (MOCVD). Surface morphology and crystal structure anisotropic behavior related to defects with a specific distribution were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM). Cathodoluminescence (CL) images and depth-profiling spectra show Basel stacking faults (BSFs) related emission at 3.42 eV, yellow band emission at 2.25 and 3.00 eV emission bands of the a-plane GaN. From the results of CL and transmission electron microscopy (TEM), the origin of the blue emission band was attributed to donor-acceptor pair (DAP) emission correlated with prismatic stacking faults (PSFs). (C) 2010 Elsevier B.V. All rights reserved.