Effect of SiN treatment on GaN epilayer quality

High-temperature GaN films were grown at 1120 degreesC and 1080 degreesC by atmospheric pressure metalorganic vapor phase epitaxy on silicon nitride (SiN)-treated sapphire using a GaN buffer layer grown at 600 degreesC. The effect of a SiN interlayer has been investigated. We have varied the silane (SiH4) flow from 4 to 20 sccm and the duration of SiN treatment from 60 s to 180 s. These layers have been characterized in-situ by laser reflectometry and ex-situ by atomic force microscopy (AFM) and low-temperature photoluminescence. AFM revealed that GaN grown with optimized SiN treatment shows a terrace-like structure with a reduced density of dislocations of about 5 x 10(8) cm-(2) compared to GaN without SiN treatment. The I-2 line is very intense with a 4 meV full width at half maximum. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.