The atomic structure of (2 x 4) reconstructed In0.48Ga0.52P(001) surfaces was analyzed by scanning tunnelling microscopy and soft X-ray photo-emission spectroscopy. The samples were grown lattice matched on GaAs(001) by metal organic vapour phase epitaxy. Immediately after growth the surfaces were passivated by a P/As-double-layer cap and then transferred to ultra-high vacuum analysis chambers for surface characterization. Under ultra-high vacuum conditions an uncontaminated, well ordered (2 x 4) reconstruction was reproducibly formed by thermal annealing for 600s at 460C. scanning tunnelling microscopy images with atomic resolution were obtained showing features typical for the mixed-dimer (2 x 4) structure as known from InP(001). This interpretation was substantiated by the appearance of two surface core level components in the soft X-ray photo-emission spectra of In 4d and Ga 3d plus one in the P 2p emission line, as expected for the mixed-dimer structure. Further annealing of the sample to higher temperatures under ultra-high vacuum degrades the surface without producing any other reconstruction. The (2 x 4) mixed dimer structure thus represents the most III-rich (least P-rich) stable (001) surface.

Surface Structure of Ordered InGaP(001) - the (2 x 4) Reconstruction. P.Vogt, K.Lüdge, M.Zorn, M.Pristovsek, W.Braun, W.Richter, N.Esser: Physical Review B, 2000, 62, 12601-4