Use of an AlN buffer layer is an enabling technique for the epitaxial growth of GaN on Si(111) substrates. The AlN growth temperature has been shown to be a significant factor that affects the properties of the GaN film and the AlGaN/GaN heterostructure. The AlN buffer grown at 1155 degreesC exhibited a uniform sized, preferred-oriented and highly faceted gr ain microstructure that led to subsequently grown AlGaN/GaN films with better quality than those on the AlN buffer grown at other temperatures. The AlGaN/GaN film quality evaluations included photoluminescence properties, surface planarity, Hall mobility and film strain.