Electronic and structural properties ofGaAs(100)(2×4)andInAs(100)(2×4)surfaces studied by core-level photoemission and scanning tunneling microscopy

Abstract

Electronic and structural properties of GaAs(100)(2x4), InAs(100)(2x4), and Sb/InAs(100)(2x4) reconstructed surfaces have been studied by synchrotron-radiation photoelectron spectroscopy and scanning tunneling microscopy (STM). Based on the difference spectrum of As 3d core-level spectra of III-As(100)(2x4), measured in different surface-sensitivity conditions, as well as the line shape of the As 3d emission from the Sb-induced (2x4) surface, we give evidence that the As 3d spectra of GaAs(100)(2x4) and InAs(100)(2x4) consist of two surface-core-level-shifted components. One of them is shifted about 0.2 eV to the lower kinetic energy from the bulk component. On the basis of the relative component intensities, this surface-shifted As 3d component is assigned to the emission from the first-layer As dimers in the established model of the (2x4) surface. The other component, shifted about 0.3 eV to the higher kinetic energy, is connected to the third-layer As-dimer site. The comparison of the core-level results between GaAs(100)(2x4) and InAs(100)(2x4) suggests that the alpha 2 phase, which has one As dimer in both the first and third atomic layers per unit cell, exists on GaAs(100)(2x4), similarly to the case of InAs(100)(2x4), as predicted in theory but not observed to date. Furthermore, the STM observation of the GaAs(100)(2x4)alpha 2 phase is reported. (Less)