Reflectance anisotropy of GaAs(100): Dislocation-induced piezo-optic effects.

Abstract

We develop a model to describe reflectance-difference (RD) spectra of zinc-blende semiconductors due to strains induced by \ensuremath{\alpha} and \ensuremath{\beta} 60\ifmmode^\circ\else\textdegree\fi{} dislocations. It is shown that near the semiconductor surface, as a result of the lost of lattice periodicity, dislocations result in an anisotropic average strain that changes the symmetry from cubic to orthorhombic, thus leading to a reflectance anisotropy. We obtain expressions for RD spectra at critical points of both \ensuremath{\Gamma} and \ensuremath{\Lambda} symmetry that predict first-derivative RD line shapes as long as the strain-induced energy shifts are small compared to spectra broadening energies. Furthermore, we report on RD spectra of semi-insulating GaAs (100) in the 1.2\char21{}5.5-eV energy range and show that such spectra comprise a component that is well described by our model. \textcopyright{} 1996 The American Physical Society.