ABSENCE OF LONG-RANGE ORDERED RECONSTRUCTION ON THE GAAS(311)A SURFACE

We have investigated the decapped GaAs(311)A surface using both scanni ng tunneling microscopy and synchrotron-radiation photoemission. While our data are in broad agreement with the structural model of GaAs(311 )A proposed in a recent study [Wassermeier et al., Phys. Rev. B 51, 14 721 (1995)], we find considerable differences in the surface order. In particular, the As dimer rows are unbroken overmuch shorter length sc ales and are highly kinked. We observe a correspondingly lower degree of anisotropy in the surface roughness than that previously reported. An (8 x 1) reconstruction was not observed. An analysis. of As 3d and Ga 3d core-level photoemission spectra suggests that surface As atoms are in only one bonding configuration while surface Ga adopts two diff erent bonding states. We discuss possible origins for the core-level s pectra surface components.