This paper investigates the growth mechanism of GaN for the hydride vapor phase epitaxy (HVPE) process in the N-2 and H-2 carrier gas ambients. Differences are observed between the surface morphologies of GaN films grown in N2 carrier gas and those grown in H2 carrier gas. It is determined that the GaN growth direction and growth rate are both affected by H-2 flow rate. In N-2 ambient, the {1 (1) over bar 0 1} facet is stable, because of the N-polarity and high dangling bond density (DB) of {1 (1) over bar 0 1} facet. On the other hand, in H-2 ambient, and the {1 (1) over bar 0 0} facet becomes stable. In this paper, this phenomenon will be explained by the atomic configuration model of the GaN wurtzite structure. (C) 2003 Elsevier B.V. All rights reserved.