GaN nano-grains were grown on nominally 0.3 degrees-miscut (0001) sapphire substrates by hydride vapor phase epitaxy (HVPE). Ordering behavior of the nano-grains was investigated by utilizing scanning electron microscopy (SEM) and synchrotron X-ray scattering. SEM images and synchrotron X-ray scattering measurement revealed that the nano-grains were nucleated with long-range ordering along the sapphire [10 (1) over bar0], which is the same as the miscut direction. With an increased growth time the nano-grains gradually coalesced, but the long-range ordering was still observed even after completion of the coalescence. (C) 2008 Elsevier B.V. All rights reserved.