Gallium nitride (GaN) nanowire (NW) arrays were grown on a gold-coated Si(1 1 1) substrate by metal-organic chemical vapor deposition (MOCVD). We grew GaN NWs at various working pressures in order to examine its effect on the growth of NWs. The synthesized GaN NWs were characterized by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) spectroscopy, photoluminescence (PL), cathodoluminescence (CL), high-resolution transmission electron microscopy (HR-TEM) and Raman spectroscopy. The GaN NWs were highly single crystalline and possess uniform smooth surfaces. The HR-TEM images and selected area electron diffraction (SAED) patterns demonstrated that the GaN NWs were single-crystal wurtzite structure. The surfaces of the GaN NWs were clean, atomically sharp and without any other phases. The PL spectra revealed sharp peaks at 366 nm with a full width at half maximum (FWHM) of 88 meV, clearly indicating that the grown GaN NWs were highly crystalline. The strong E2 (high) phonon line appeared at 567 cm-1 in the Raman spectrum reflects that the characteristics of wurtzite structure of GaN NWs. © 2009 Elsevier B.V. All rights reserved.