Reflectance Difference Spectra Calculations of GaAs(001) As- and Ga-rich Reconstruction Surface Structures

The reflectance difference (RD) spectra of nine GaAs(001) surface reconstructions, (2×4)β2, (2×4)α, (2×4)γ2, (2×4)β1, (2×4)γ1 and c(4×4) reconstructions on As-rich surface and (4×2)β2, (4×2)α and (4×2)β1 reconstructions on Ga-rich surface, were studied by using the nearest-neighbor s p 3 s * tight-binding method. The surface atomic positions and the tight-binding interaction parameters were obtained by the ab inito pseudopotential calculations. We found that the RD spectra have considerably different features between As- and Ga-rich surface reconstructions. The RD spectra of As-rich surfaces are mainly understood by transitions between top As-dimer states, while the RD spectra of Ga-rich surfaces are explained by the surface electronic states resulting from the sinkage of surface Ga atoms into bulk layers. These calculations are compared with the results of recent experiments.