Abstract
We report on a theoretical model to describe reflectance-difference (RD) spectra for the (110) surface of zinc-blende semiconductors due to anisotropic strains induced by 60\ifmmode^\circ\else\textdegree\fi{} dislocations. We obtain expressions for the RD spectrum at critical points of \ensuremath{\Gamma} symmetry that predict second-energy-derivative RD line shapes as far as the strain-induced energy shifts are small compared to spectra broadening energies. The second-derivative line shape contrasts with the first-derivative line shape observed previously for the GaAs(001) surface. We further report on experimental RD spectra of semi-insulating GaAs(110) in the 1.2--1.6 eV energy range and show that such spectra comprise a component that is well described by our theoretical model. Results obtained in the present work prove the existence of dislocation-induced components in RD GaAs spectra. We expect that they will contribute to further development of RD spectroscopy as a surface and near-surface optical probe for zinc-blende semiconductors.
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