An iodine vapor phase epitaxy (IVPE) system has been designed and built to grow high quality thick gallium nitride film at the growth rate up to 80 mu m/h with the deposition temperature of 1050 degrees C and the pressure of 200 torr. Numerical and experimental studies have been performed to investigate heat and mass transport and reaction phenomena in a vertical reactor. Geometrical parameters and operating conditions are optimized to achieve high and uniform GaN deposition rate. Gas phase and surface reactions in the growth chamber have been analyzed thermodynamically and kinetically, and primary transport species and important reactions are identified. The rate expressions for different surface reactions are determined and their contributions to the GaN deposition rate are studied for different V/III ratios. The sticking probability of the main reactants and adsorption activation energy are calculated. (C) 2007 Elsevier Ltd. All rights reserved.