• Au/Ni catalyst;
  • GaN;
  • nanowires;
  • NH3/N2 flow rate

GaN nanowires (NWs) were grown on Ni- and Au/Ni-coated Si (100) substrate by chemical vapor deposition via reaction of metallic Ga and NH3. It was found that the Au/Ni layer tends to form liquid droplets with more uniform size distribution and regular spherical shape under annealing, which facilitates the growth of straight and long NWs. The effects of NH3/N2 ratio on NW growth are different for Ni and Au/Ni catalysts, due to the competition between the vapor–solid (VS) and vapor–liquid–solid (VLS) growth. The XRD analyses indicate that with decreasing NH3 flow rate, [0001] axial growth becomes dominant with the formation of NiGa4 catalyst.