Investigation of catalyst-assisted growth of nonpolar GaN nanowires via a modified HVPE process†
The growth of nonpolar GaN nanowires along the  orientation has been demonstrated via a modified hydride vapor phase epitaxy (HVPE) process using GaCl3 and NH3 as precursors. The morphology and structure evolution as a dependence of the growth parameters was thoroughly studied to elucidate the nucleation and crystallization of nonpolar GaN nanowires. It has been found that the V/III ratio and temperature are critically important for the formation of high-quality nonpolar GaN nanowires. The existence of a cubic GaN (c-GaN) transition layer between the Au catalyst and hexagonal GaN (h-GaN) nonpolar nanowires was demonstrated by high-resolution transmission electron microscopy (HRTEM) characterization, which plays an important role in the initial nucleation of nonpolar GaN nanowires and the formation of stacking faults (SFs) in the GaN nanowires grown at lower temperature. Optical investigations show that the defect-related visible emission of nonpolar GaN nanowires is closely related to the growth process and can be selectively tailored. The synthetic strategy using GaCl3 as the Ga precursor to study the vapor phase epitaxy process in this work will provide a simple and efficient approach to obtain nonpolar GaN nanowires and will thus pave a solid way for fundamental research on high-quality nonpolar GaN nanowires in optoelectronic nanodevices.