Optical anisotropy of (001)-GaAs surface quantum wells

We report a reflectance difference spectroscopy (RDS) study of the optical anisotropy of GaAs:(001) Surface quantum wells consisting of a thin GaAs layer (3-30 nm thick) embedded between an arsenic reconstructed surface and an AlAs barrier. The RDS spectra display anisotropic contributions from the free Surface and from the GaAs/AlAs interface. By comparing RDS spectra for the c(4x4) and (2x4) Surface reconstructions, we separate these two contributions, and demonstrate that the anisotropy around the E-1 and E-1 + Delta(1) transitions comprises a component originating from modifications of bulk states near the surface. The latter is attributed to anisotropic strains induced by the surface reconstruction. The experimental data Lire well described by a model for the RDS response of the multilayer structures, which also takes into account the blue energy shifts and the changes in oscillator strength of the E-1 and E-1 + Delta(1) transitions induced by quantum-well confinement