The optical anisotropy of c(4 x 4), (2 x 4), (2 x 6) and (4 x 2) reconstructed GaAs(001) surfaces was calculated from first principles. It consisted of surface structure-dependent features originating from electronic transitions in the uppermost surface layers and of anisotropy peaks close to the E1 and E0′/E2 bulk critical point energies. The latter contributions were nearly structure independent and arise from transitions between surface-modified bulk electronic states. For the smaller reconstructions the influence of surface electric fields on the optical anisotropy was studied. It was found that the linear electro-optic effect modifies mainly the optical anisotropy from the bulk atomic layers, resulting in changes of the reflectance anisotropy spectroscopy signal which were strongly reconstruction dependent, however. Changes in the atomic relaxation due to surface electric fields were less important for the modification of the optical signal than the polarization of the electron wave functions.

Interplay of Surface Reconstruction and Surface Electric Fields in the Optical Anisotropy of GaAs(001). W.G.Schmidt, F.Bechstedt, W.Lu, J.Bernholc: Physical Review B, 2002, 66[8], 085334 (6pp)