We investigated the effects of growth pressure on AlGaN growth and material properties of GaN:Mg using a multiwafer metal organic vapor phase epitaxy (MOVPE) reactor. We developed a three-layer laminar flow gas injection reactor to control the pre-reaction between adducts in GaN MOVPE. Using this reactor, we could grow Al0.09Ga0.91N at a growth rate of 0.8 mum/h, and GaN:Mg with a carrier concentration of 1.4 x 10(18) cm(-3) at a growth rate of 3.5 mum/h at atmospheric pressure. While we grew Al0.24Ga0.76N at a growth rate of 0.8 mum/h at 300 Torr, we found that the hole carrier concentration of GaN:Mg grown at 300 Torr is more than one order of magnitude lower than that of GaN:Mg grown at atmospheric pressure. (C) 2004 Elsevier B.V. All rights reserved.