Increasing demand for high brightness LEDs for LCD TV backlighting and solid-state lighting requires MOCVD growth of GaN at high growth rates (> 5 mu m/h) with high crystalline quality in mass production reactors. Understanding the MOCVD growth parameters on the quality of GaN materials and growth efficiency are important for quickly setting up process windows for the optimization and qualification of new LED growth processes. We have investigated the effects of N(2)/H(2) ratio, N(2)/NH(3) ratio, and growth temperature on the growth efficiency, crystal quality, morphology, yellow-band emission (YE), and sheet resistance of un-doped GaN epitaxial layers using design of experiment (DOE) methodology. Our results indicate that high growth temperature (at 1080 degrees C) and low N(2)/H(2) ratio (set at 0.5 in the DOE) were the common factors for achieving better crystal quality, smoother surface, and lower YE intensity in GaN epitaxial layers, as well as for obtaining higher growth efficiency in MOCVD of GaN. (C) 2010 Elsevier B.V. All rights reserved.