Gallium nitride nanostructures continue to attract great interest due to their applications in optoelectronic devices, high-power/high temperature electronics, and nanosensing. This paper presents a detailed study of GaN nanowire morphology changes stemming from the process parameters by chemical vapor deposition using Ga and NH3 as source materials on SiO 2/Si substrate. Various types of catalyst materials, including gold, nickel, silver, cobalt and iron, have been used for growth runs at 1100°C under H2 as carrier gas. Dramatic shifts in nanowire morphology have been observed in accordance with the variations in process parameters. In addition, nanowire FET devices have been fabricated. A unique annealing scheme has been implemented to improve contacts between nanowires and gold electrodes, which resulted in very consistent electrical measurements. The GaN nanowire diameters are mostly in the range of 15 nm to 50 nm and lengths up to hundred microns. The grown nanowires and devices have been characterized by SEM, XRD, TEM, and semiconductor parameter analyzer.