Growth and optical properties of gallium nitride nanowires produced via different routes

Several vapor phase processes for the preparation of GaN nanowires, such as chemical vapor deposition (CVD), direct reaction (DR), and hydride vapor phase epitaxial growth (HVPE), have been previously reported. To determine the most appropriate route for fabrication and engineering of GaN nanowires, we prepared nanowires via the three aforementioned routes and characterized their microstructures and photoluminescence (PL) properties. All prepared nanowires were single-crystalline, whowing well-defined crystal structure in X-ray diffraction and transmission electron microscopic analyses. However, high-quality nanowires could most readily be obtained by DR. Large-scale and selective area growth of nanowires could most readily be achieved by CVD and HVPE. PL spectra for the nanowires prepared by HVPE showed a red-shifted center wavelength and wider full width-half maximum (FWHM) value as compared to those prepared by DR or CVD. This indicates the presence of unknown impurities and/or defects in the nanowires prepared by HVPE. Our results indicate that high-quality nanowires can be prepared by DR and CVD, while large-scale selective growth can be achieved by CVD and HVPE.