In this work we are presenting growth results of thick gallium nitride (GaN), numerical modeling and optimization of a vertical hot-walled halide vapor-phase epitaxy reactor. Using a simulation model, the growth rate and thickness uniformity of the GaN layers have been predicted and optimized. The simulation results have been correlated with experiments to verify the model. Using constant precursor flows, the average growth rate over a 2 in substrate was increased with a factor of four by only optimizing the composition of N-2 and H-2 in the carrier gas and the carrier gas flow rates. With a simple sticking model, assuming Ga mass transport-limited growth, the growth rate and thickness uniformity could be estimated. Photoluminescence mapping of the grown layer shows that the layers have excellent optical properties and a high degree of uniformity. (C) 2007 Elsevier B.V. All rights reserved.