For the epitaxial growth of GaN on Si substrate the buffer layer is essential as an anchor to achieve nucleation and duplicate orientation. In this study, AlN layer was used as a buffer layer for the growth of GaN on Si substrate and the effect of crystal quality of an AlN buffer layer on the growth characteristics of GaN was investigated. To compare the effect of various AlN buffer layers on the GaN growth we prepared three types of AlN using MOCVD, MOMBE and RF-sputtering, respectively. Then the epitaxial growth of GaN by MOCVD using high quality AlN buffer layer was identified. The AlN epitaxial layer has reduced the misorientation of both in-plane and out-plane between GaN and AlN layer at the initial growth stage. It implies that GaN can be epitaxially grown in case of using epitaxially grown AlN buffer layer irrespective of growth method. (C) 2002 Elsevier Science B.V. All rights reserved.