This study demonstrates improvement of crystalline quality of a-plane GaN by growing it on a porous GaN template fabricated by in situ etching of a first GaN film using hydrogen and ammonia gases at 1150 degrees C in a metal organic chemical vapor deposition (MOCVD) reactor. Photoluminescence (PL) and high-resolution X-ray diffraction (HR-XRD) measurements show that the crystalline quality of the GaN film re-grown on the porous GaN template was superior to the quality of the initially grown GaN film. This study demonstrates a simple, short procedure for growing high quality a-GaN using a single MOCVD tool without ex situ processes. (C) 2010 Elsevier B.V. All rights reserved.