A combination of experimental and computational fluid dynamics-based reactor modeling studies were utilized to study the effects of process conditions on GaN nanowire growth by metalorganic chemical vapor deposition (MOCVD) in an isothermal tube reactor. The GaN nanowires were synthesized on (0 0 0 1) sapphire substrates using nickel thin films as a catalyst. GaN nanowire growth was observed over a furnace temperature range of 800-900 degrees C at V/III ratios ranging from 33 to 67 and was found to be strongly dependent on the position of the substrate relative to the group III inlet tube. The modeling studies revealed that nanowire growth consistently occurred in a region in the reactor where the GaN thin-film deposition rate was reduced and the gas phase consisted primarily of intermediate species produced by the reaction and decomposition of trimethylgallium-ammonia adduct compounds. The GaN nanowires exhibited a predominant [1 1 (2) over bar 0] growth direction. Photoluminescence measurements revealed an increase in the GaN near-band edge emission intensity and a reduction in the deep-level yellow luminescence with increasing growth temperature and V/III ratio. (C) 2009 Elsevier B.V. All rights reserved.