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Reflectance Difference (RD/RAS) spectroscopy has emerged in the last two decades as a sensitive probe for the study of surface and surface-induced phenomena in zincblende semiconductors. This spectroscopy measures the difference in reflectivity between two mutually orthogonal polarizations and it is thus specific to semiconductor regions with symmetries lower than cubic. Photoreflectance-difference (PRD) spectroscopy is a technique closely related to RD spectroscopy that measures the difference between two photoreflectance spectra, one with linearly-polarized light and the other with non-polarized light. In contrast to RD spectroscopy, PRD spectroscopy is specific to reflectance anisotropies of electro-optic origin. In this paper we will discuss the application of both RD and PRD spectroscopies to the study of strain-induced optical anisotropies in zincblende semiconductors. We will present a theoretical line shape model for both RD and PRD spectra that describes with high accuracy the experimental spectra. Results show the high sensitivity of these techniques for the study of piezo-optical properties of zincblende semiconductors. Furthermore, results to be discussed should prove to be useful in the identification of strain-induced contributions to RD spectra that are know to comprise components with a number of physical origins.

Reflectance difference spectroscopy (RDS/RAS) constitutes a very sensitive tool for the study of the optical properties of semiconductors. RDS spectra comprise several components of different physical origins. One of these components is the strain induced by the surface. In the present work, we report RD spectra measured on GaAs at room temperature at around E1 and the E1+Δ1 transitions. Two cases were studied, the surface strains induced by the c (4× 4) reconstruction and by the vacancies generated by the annealing of semi insulating GaAs crystal. Fits to the line shape of the c (4× 4) reconstructed and annealed spectra were performed by using a surface strain component for one‐electron and discrete‐exciton lineshapes respectively. The character of the fits were interpreted by estimating the piezoelectric field induced by surface strain. For the c (4× 4) surface the strength of the field partially quenches the exciton while for the annealing surface this field is fifty times lower, and an excitonic lineshape is expected.We also inferred that the RD spectra include a component related to surface roughness. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)