Surface electronic structure of GaAs(001)-(2×4): Angle-resolved photoemission and tight-binding calculations

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Abstract
We have carried out an experimental and theoretical study of the surface-energy-band structure of the As-stable GaAs(001)-(2×4) reconstruction. Angle-resolved photoemission measurements with the use of synchrotron radiation at LURE, Orsay, have been performed on surfaces which were grown in situ by molecular beam epitaxy. Measurements made at high-symmetry points and along symmetry lines of the surface Brillouin zone show weakly dispersing dangling-bond-like surface states in the energy range between - 1.6 eV and the top of the valence band, and a nearly dispersionless state near - 3 eV. To clarify the origin of these states, we have applied the scattering theoretical method on the basis of an empirical tight-binding description of the GaAs bulk crystal to the ideal (1×1) As-terminated surface and to a (2×1) asymmetric As-As dimer model. The principal effect of the reconstruction is the introduction of a new dimer-related state at - 3.5 eV. In addition in the energy range near the top of the projected bulk bands, dangling-bond states with a significant in-plane component are found. Although we do not observe a direct one-to-one correspondence between experiment and theory, the essential features of an asymmetric As-As dimer are established.