This paper presents systematic study of an improved vapor-phase expitaxy system-a halide vapor transport epitaxy (HVTE) system [D.F. Bliss, V.L. Tassev, D. Weyburne, J.S. Bailey, J. Crystal Growth 250 (2003) 1]. A numerical model has been developed, which is capable of describing multi-component fluid flow, gas/surface chemistry, conjugate heat transfer, and species transport, and it has been applied to the HVTE system for optimal design. The investigation has been conducted to study the effects of the gas-phase reactions, the reactor wall deposition, the adduct boat and the three-zone furnace temperature, the carrier gas flow rate and the distance between the adduct boat and the substrate on the aluminum nitride deposition rate/deposition uniformity. (c) 2006 Elsevier B.V. All rights reserved.