Strain induced optical anisotropies in zincblende semiconductors

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 photo reflectance 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. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.