First-principles study of In, Ga, and N adsorption on In_xGa_(1-x)N (0001) and (0001) surfaces

摘要

We consider the adsorption of In, Ga, and N on the (0001) and (0001) surfaces of In_xGa_(1-x)N as a function of the experimentally controllable chemical potentials of the constituents in the gas phase and the composition of the substrate, x. We first determine the equilibrium composition and reconstruction of these surfaces on InN and GaN substrates using density-functional calculations. We propose a method to estimate the average composition of the surface of the solid solution or the phase separated alloy. We find that under most conditions, the (0001) and (0001) surfaces of In_xGa_(1-x)N are terminated with at least one In adlayer for all substrate conditions x. This result is consistent with the prediction that In may serve as a surfactant for the growth of In_xGa_(1-x)N over the entire composition range. The proposed method for determining the surface composition of an alloy over a wide composition range should be applicable to a wide range of materials.