Reflection high-energy electron diffraction and atomic force microscopic studies were made of the growth of AlN by molecular beam epitaxy onto sapphire (00•1) substrates. The surface morphology and reconstruction were monitored as a function of temperature, using initially nitrided substrates. A (2 x 2) reconstruction was found after growth using 2 different procedures: cooling, or maintaining at high temperatures for long periods. During subsequent growth, this (2 x 2) reconstruction could be maintained for some time before it reverted to a (1 x 1) pattern. A study was also made of the effects, upon reconstruction, of the post-growth deposition of Al at high temperatures onto the AlN surface after growth. By desorbing the excess Al, the (2 x 2) surface reconstruction recovery time was found to be directly proportional to the Al deposition time. This strongly suggested that the (2 x 2) reconstruction was intrinsic to AlN.

Surface Reconstruction Patterns of AlN Grown by Molecular Beam Epitaxy on Sapphire. C.S.Davis, S.V.Novikov, T.S.Cheng, R.P.Campion, C.T.Foxon: Journal of Crystal Growth, 2001, 226[2-3], 203-8