The requirements for mass production of electronic and optoelectronic devices call for the expansion of MOCVD reactor capacity by increasing the number of wafers and the wafer size. Today, MOCVD reactors with capacities of 24 x 2 in. and 8 x 4 in. are readily available. Growth experiments on 4-in. wafers, however, require careful process and reactor hardware design since the effects related to strain and the resultant wafer bow are more pronounced in larger wafers. We have investigated the design criteria for MOCVD hardware and developed a tool for the straightforward optimization of the hardware to a given device structure and process. Morphological and electrical studies show that samples with off-cuts of 0.3 degrees and 0.4 degrees from the c-plane offer the broadest temperature process window for the growth of GaN. (c) 2006 Elsevier B.V. All rights reserved.