COMPARISON OF AS-RICH AND SB-TERMINATED GAAS(100)(2X4) RECONSTRUCTIONS

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