High temperature (HT)-GaN films inserted with low temperature (LT)-GaN interlayers were grown on (0 0 0 1) sapphire substrates by alternate supply of metal alkyls (trimethylgallium (TMG) and trimethylaluminum (TMA)) and ammonia (NH3) in an inductively heated quartz reactor operated at atmospheric pressure. Based upon the results of scanning electron microscopic (SEM) observations, it was found that the mosaic structure in a thin HT-GaN film could be eliminated by using a LT-GaN interlayer. The HT-GaN film inserted with a LT-GaN interlayer having optimized thickness shows an enhanced room temperature (RT) photoluminescence (PL) intensity of the near band-edge emission by more than one order of magnitude compared with that of a HT-GaN film without any LT-GaN interlayer. The results of transmission electron microscopy (TEM) and double-crystal X-ray diffractometry (DCXRD) indicate that improvement in PL results is primarily due to the elimination of mosaic structure in the GaN film. Moreover, the insertion of LT-GaN interlayers in HT-GaN films was found to reduce the compressive strain in the HT-GaN films. (C) 2003 Elsevier B.V. All rights reserved.