Theoretical study on the influence of surface hydrogen coverage on the initial growth process of AlN(0001) surfaces

The adsorption processes of group-V sources used in metalorganic vapor phase epitaxy (MOVPE) and hydride vapor phase epitaxy (HVPE) were investigated using first-principle calculations based on the density functional theory (DFT) to understand the initial growth process of AlN(0001). To examine the influence of surface hydrogen coverage on the initial growth process, the ideal surface and a reconstructed surface with an adsorbed 0.75 monolayer of hydrogen were used as the initial surface structures. NH3 and NH2 generated by the decomposition of NH3 were considered as group-V sources. From the calculations, the influence of surface hydrogen coverage on the initial growth process of AlN(0001) surfaces in vapor phase epitaxy was clarified. It was revealed that surface hydrogen coverage does not have an effect on adsorption of NH3, whereas NH2 was affected by hydrogen on the surface. It was also demonstrated that the adsorption energies for NH3 and NH2 on the ideal and reconstructed GaN(0001) surfaces are smaller than those on the ideal and reconstructed AlN(0001) surfaces. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim