GaN and AIN films were grown on (111) and (001) Si substrates by separate admittances of trimethylgallium (or trimethylaluminum) and ammonia (NH3) at 1000degreesC. A high temperature (HT) or low temperature (LT) grown AIN thin layer was employed as the buffer layer between HT GaN (or HT.AIN) film and Si substrate. Experimental results show that HT AIN and HT GaN films grown on the HT AIN-coated Si substrates exhibit better crystalline quality than those deposited on the LT AIN-coated Si substrates. Transmission electron microscopy (TEM) of the HT GaN/HT AIN buffer layer/(111)Si samples shows a particular orientation relationship between the (0001) planes of GaN film and the (111) planes of Si substrate. High quality HT GaN films were achieved on (111) Si substrates using a 200 A thick FIT AIN buffer layer. Room temperature photoluminescence spectra of the high quality HT GaN films show strong near band edge luminescence at 3.41 eV with an emission linewidth of similar to 110 meV and weak yellow luminescence. (C) 2002 Elsevier Science B.V. All rights reserved.