Gold catalyst initiated growth of GaN nanowires by MOCVD

Our study shows the impact of the process parameters V/III ratio, pressure and temperature on growth and morphology of GaN nanowires (NWs) synthesized by an Au‐initiated vapour‐liquid‐solid mechanism on a sapphire substrate. We confined a temperature window for successful GaN NW growth and show how the variation of reactor pressure changes the NW morphology. Using a very low V/III ratio, NW tapering, which was observed for higher V/III ratios, could be avoided. The optimization of these process parameters led to non‐tapered GaN NWs, aligned perpendicular to the substrate. Further evaluation by scanning electron microscopy showed a high density (∼3·109/cm2) of hexagonal c‐plane GaN NWs having diameters of 60 ± 9 nm. Transmission electron microscopy revealed single‐crystalline NWs without threading dislocations but some stacking faults. The use of a very low V/III ratio was found to be important for the successful selective growth and, most interestingly, led to a difference in NW and gold catalyst droplet diameter. For chemical analysis of the NW and its catalyst droplet, electron energy loss spectroscopy was employed confirming gold as the catalyst material (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)