Influence of hydrogen coverage on Si(1Â 1Â 1) substrate on the growth of GaN buffer layer

The influence of hydrogen coverage on a Si(1 1 1) substrate on the initial growth of a GaN buffer layer was investigated using Ga and Al adsorption energies obtained by ab initio calculations. It was found that absolute values of the adsorption energies of Ga and Al atoms increased as the hydrogen coverage on the substrate surface decreased. Moreover, it was found that the absolute value of Al adsorption energy was larger than that of Ga in any case. These results suggest that it is important to control the substrate surface condition and carrier gas for the growth of a GaN buffer layer on a Si substrate, though an AlN buffer layer can be grown even under H2 ambient.