In this paper, we report on a combined modeling and experimental analysis of the GaN deposition behavior in the horizontal AIX 200/4 RF-S reactor. The study was aimed at revealing the effect of the variations of the operating parameters on the growth rate and uniformity. Variations of the trimethylgallium and hydride flow rates, changes in the composition of the mixture supplied through the hydride inlet, and the total flow redistribution between two reactor inlets have been considered. To get an insight into the mechanisms governing the measured GaN growth rate alterations, a detailed three-dimensional modeling has been used. Application of the reactor model accounting for important features of the reactor design and utilizing advanced chemical models has allowed us to reproduce fairly well experimental data and to draw conclusions on the mechanisms governing the deposition process. (C) 2003 Elsevier B.V. All rights reserved.