High Al-content AlxGa1-xN epilayers with x = 0.62-0.64 were grown on AIN buffer by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). As growth temperature of initial AIN buffer increased, the full-width at half-maximum (FWHM) of the AlGaN (002) rocking curves decreased from 942 to 637 arcsec. Meanwhile, vacuum ultraviolet (VUV) photoluminescence (PL) spectroscopy showed that band edge exciton transition was greatly intensified, while deep level radiative recombination especially peaked at 304 nm was effectively suppressed. They were ascribed to the reducing of threading dislocations (TDs) in the AlGaN epilayers. (c) 2007 Elsevier B.V. All rights reserved.