Atomic ordering in InxGa1-xAs alloy thin films:: Action of surfactants -: art. no. 045304

The effect of a surfactant (b and Bi) ordering of alloy thin films of (n, Ga) is studied using ab initio total energy calculations based on the density functional theory; ultrasoft pseudopotentials are applied in a plane-wave basis. Anion-terminated thin films of (n, Ga) As on the InP [001] substrate are assumed in the ordered CuPt-B geometry, with the beta2(2x4)-reconstructed surface. The energetics of disorder in the mixed cation plane (In, Ga) is examined quantitatively, comparing the films with clean surfaces and surfaces covered by surfactant. The analogous systems (In, Ga)P:(As, Sb, Bi) are studied at the same time, for comparison and in order to establish the differences in the action of the same surfactants. The mechanism of the action of different surfactant atoms is discussed in terms of the reduction of the strain in the subsurface layers. The variation of the surface formation energy with chemical potentials is compared at different coverages and for various positions of the surfactant atoms.