Structural fingerprints in the reflectance anisotropy spectra ofInP(001)(2×4)surfaces

The reflectance anisotropy has been calculated from first principles for a series of recently proposed structural models of the $\mathrm{InP}\mathrm{}\left(001\right)(2\mathrm{}\times 4)$ surface. The features of the calculated spectra are related to specific surface bonding configurations. We find a pronounced negative anisotropy around 1.7 eV linked to transitions between σ-like In-In bonding states and empty dangling bonds localized at the surface cations. The strength of that anisotropy is directly related to the number of In-In bonds at the surface. This explains the gradual change of the corresponding measured anisotropy in that energy region, depending on the growth conditions. Positive anisotropies at higher energies arise from transitions between P-P dimer related states and surface resonances. Additionally we find derivativelike features at the energy of the $E_1$ peak that depend only weakly on the surface structure and stoichiometry. In conjunction with the experimental data, our results indicate that the (2×4) reconstructed InP(001) surface features In-In bonds along [110] and P-P dimers parallel to $\left[11¯0\right],$ respectively. The relative number of these bonds varies with the growth conditions.