Growth of high-quality and crack free AlN layers on sapphire substrate by multi-growth mode modification

Various procedures, such as using a buffer layer or multi-growth mode modification, were investigated for the growth of AlN layers on sapphire substrate at high temperatures by metalorganic vapor phase epitaxy. Even though the top AlN layers were grown under the same conditions, the each crystalline quality was different. There is a clear relationship between the strain during growth and the quality of AlN films. AlN grown under the least strain shows the highest quality. Furthermore, it was found that cracks were suppressed by multi-growth mode modification.