High-Quality Thick GaN Overgrown on an Array of SiO2 Nanomasks by HVPE

We report nanoepitaxy of thick GaN films by hydride vapor-phase epitaxy (HVPE) using a uniform array of SiO 2 nanomasks that were prepared by electron-beam evaporation and anodic aluminum oxide membranes. The controllable size and density of the SiO 2 nanoisland mask were about 65 nm and 10 10 cm -2 , respectively. Subsequent overgrowth takes place selectively on the exposed GaN surface without the SiO 2 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.