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Abstract:
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.
