Electroreflectance polarization study of valence-band states in ordered Ga0.5In0.5P

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Abstract
Anisotropic optical transitions in an ordered Ga0.5In0.5P alloy semiconductor have been studied by electroreflectance (ER) polarization spectroscopy. The atomic ordering of column-III sublattices causes a splitting of the valence-band maximum into two doubly degenerated levels at k=0. The ER spectra reveal signals originated from the Γ6c-Γ4v, Γ5v and Γ6c-Γ6v transitions caused by the ordering. The [110] and [11̄0] ER signals due to the Γ6c-Γ6v transition show strong anisotropic characters of their intensity and line shape. On the other hand, the signal due to the Γ6c-Γ4v, Γ5v transition changes only in the intensity by the polarization direction. The ER intensities measured at various polarization angles follow the theoretically derived trends based on the selection rule for electronic-dipole transitions in the ordered crystal.