A study was made of the growth of AlN by molecular beam epitaxy on sapphire substrates using reflection high energy electron diffraction and atomic force microscopy. The surface morphology and reconstruction were monitored as a function of temperature using initially nitrided sapphire substrates. A (2 x 2) reconstruction was obtained on AlN after growth using two different procedures; either by cooling or by retaining at high temperature for an extended period of time. During the subsequent growth of AlN 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 influence 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