Optical-reflectance anisotropy in epitaxial metastable (GaAs)1-x(Si2)x(001) alloys: A probe for the zinc-blende to diamond structural transition

Anisotropy in the above-band-gap optical reflectance along the [110] and [11»0] directions has been used to investigate long-range atomic ordering in metastable epitaxial (GaAs)1-x(Si2)x(001) alloys as a function of Si concentration x. The amplitude of the differentiated reflectance-difference signal was found to decrease monotonically with increasing x and reach zero, corresponding to the critical concentration for the zinc-blende to diamond transition, at x 0.37, consistent with x-ray-diffraction results. The highest sensitivity in the optical-anisotropy spectra was obtained in the spectral region near the E0 critical point (4.5 eV in GaAs). © 1991 The American Physical Society.

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