Hexagonal GaN thin films were grown on Si(111) substrates using single molecular precursor by high vacuum metalorganic chemical vapor deposition at various temperatures from 600 to 800 degreesC and pressures in the range of 2 X 10(-6) to 2 X 10(-5) Torr. We first developed and synthesized the single molecular precursor of diethylazidogallium methythydrazine adduct, [(Et)(2)Ga(N-3)HzMe], with the objectives of reducing carbon content in the GaN films and lowering growth temperatures. Results of x-ray diffraction (XRD), x-ray pole figure, and x-ray photoelectron spectroscopy measurements showed that this approach yielded a single crystalline GaN thin film of [0002] orientation with relatively low carbon content. Ga-rich compositions Ga:N of 1:0.92 were obtained at a temperature of 750 degreesC and a pressure of 2 X 10(-6) Torr. However, for growth temperatures below 700 degreesC, we found the films to be polycrystalline. Scanning electron microscope (SEM) and atomic force microscope (AFM) images showed that the as-grown GaN films have a smooth surface morphology. Based on XRD, AFM, and SEM results, we identified effects of deposition temperature and pressure on the growth rate and crystallinity, and can suggest that our deposition process is governed by diffusion rate control. Optical properties were investigated by photoluminescence, which revealed an emission peak at 3.40 eV with a full width at half-maximum of approximately 100 meV for a GaN film grown at 750 degreesC and 2 X 10(-6) Torr. (C) 2004 American Vacuum Society.