AlN nucleation and buffer layers have been grown with different flux ratio by molecular beam epitaxy on sapphire. Thick AlN on top of a nucleation layer grown with flux ratio exhibited deep hexagonal holes (diameter 100–200 nm, density ). Investigation of the nucleation layer surface revealed that the holes were formed already during the nucleation. The formation of holes in AlN buffer layers could be avoided by using a N-rich nucleation layer. It is demonstrated that the holes in AlN buffer layers can be effectively avoided choosing a N-rich nucleation layer growth and then switch to flux ratio for buffer layer growth. The two-step AlN growth gave high quality AlN, with excellent crystalline quality and smooth surface.
Influence of flux ratio during nucleation layer growth on the structural properties of AlN grown on sapphire by molecular beam epitaxy
J. F. Fälth, S. K. Davidsson, X. Y. Liu, T. G. Andersson; Influence of flux ratio during nucleation layer growth on the structural properties of AlN grown on sapphire by molecular beam epitaxy. Appl. Phys. Lett. 17 October 2005; 87 (16): 161901. https://doi.org/10.1063/1.2093923
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