A nano-holes patterned GaN-on-patterned sapphire substrate template has been developed to reduce the threading dislocation (TD) density in homoepitaxy GaN layer grown by plasma-assisted molecular beam epitaxy. The grown layers characterized by high resolution x-ray diffraction, photoluminescence, and cross-section transmission electron microscopy confirm that the TD density of GaN epilayer has been successfully reduced an order of magnitude to similar to 10(7) cm(-2) by optimizing the depth and coverage area percentage of patterned nano-holes. (C) 2015 Elsevier B.V. All rights reserved.