Comparison of As-rich and Sb-terminated GaAs(100)(2x4) reconstructions

We present results of accurate first-principle total-energy calculations on Sb-terminated GaAs(100)(2 x 4) surfaces. We discuss the atomic structures and stability of several interface geometries in comparison with results for As-rich GaAs(100)(2 x 4) reconstructions. AU interfaces are characterized by similar structural elements as Sb dimers with a length of about 2.9 Angstrom, dimer vacancies and a nearly planar configuration of the three-fold coordinated second-layer Ga atoms. They are rather similar to the corresponding As-rich surface phases. In analogy to recent findings for the As-rich (2 x 4) surface reconstructions we favour two-Sb-dimer structures over the three-dimer model.