Effect of strain on atomic ordering and action of surfactants in ternary alloy thin films

Effect of surfactant (Sb) on ordering in alloy thin films of (In,Ga)P and (In,Ga)As, lattice mismatched with the substrate, is studied using ab initio total energy calculations based on the density functional theory. Anion-terminated thin films of (In,Ga)As on the GaAs [001] substrate and (In,Ga)P on the GaP [001] substrate are assumed in the ordered CuPt-B geometry, with the beta2(2x4)-reconstructed surface. The results are compared with the previous calculations on the same alloy layers but lattice matched with the substrate. Consequences of strain (due to lattice mismatch) on the ordering in these films, bare and covered with surfactant, are discussed in relation with surface and interface geometries and in terms of the surface formation and interchange energies.