We have studied the effect of annealing AIN buffer layers on the properties of subsequently grown GaN layers. The AIN buffer layer was deposited on a Si(111) substrate by using RF sputtering, and different samples were then annealed at temperatures of 700 degrees C, 800 degrees C, and 900 degrees C. Thick GaN was grown using a hydride vapor phase epitaxy (HVPE) system for 1 hour at 1050 degrees C with the resultant thickness being 150 mu m. The morphologies of the AIN and the GaN layers were ...