A quantitative estimate of the In/Ga surface concentration ratio in ultra-thin InGaAs strained layers, grown onto a GaAs(001) substrate by means of molecular-beam epitaxy, was obtained by using grazing-incidence X-ray diffraction and diffuse-scattering methods. A commensurate 2 x 3 reconstruction was interpreted as being due to cation ordering in the surface unit cell; fixing the surface composition at a value of In2/3Ga1/3As. Incommensurate 2 x n reconstructions, where n was less than 3 or greater than 3 were described in terms of In-depleted or In-enriched surface layers, respectively, and were characterized by a statistical distribution of faults in the ideal 2 x 3 atomic arrangement. A unique correspondence between the incommensurability parameter and the In surface fraction was established, within a definite temperature range of 450 to 490C, on the basis of the diffuse scattering distribution.

Stoichiometry and discommensuration on InxGa1-xAs/GaAs(001) reconstructed surfaces Y.Garreau, K.Aïd, M.Sauvage-Simkin, R.Pinchaux, C.F.McConville, T.S.Jones, J.L.Sudijono, E.S.Tok: Physical Review B, 1998, 58[24], 16177-85