We report nanoepitaxy of thick GaN films by hydride vapor-phase epitaxy (HVPE) using a uniform array of SiO2 nanomasks that were prepared by electron-beam evaporation and anodic aluminum oxide membranes. The controllable size and density of the SiO2 nanoisland mask were about 65 nm and 10(10) cm(-2), respectively. Subsequent overgrowth takes place selectively on the exposed GaN surface without the SiO2 masks to the formation of the continuous layer. High-resolution X-ray diffraction shows reduction of threading dislocations in the overgrown layers. Improved optical property and significant stress relaxation in the epilayer are demonstrated by photoluminescence and micro-Raman spectra. The deposition method is a more promising technique for obtaining freestanding GaN substrates with high-quality and uniform features. (C) 2008 The Electrochemical Society. [DOI: 10.1149/1.2999377] All rights reserved.