PHOTOREFLECTANCE SPECTROSCOPY OF MICROSTRUCTURES

This chapter describes the application and flexibility of modulation spectroscopy, particularly electroreflectance (ER) and photoreflectance (PR), to study artificially structured materials (ASMs). The chapter explains the way measurements on microstructures have helped understand the properties of ASM and of the modulation mechanisms involved in electromodulation spectroscopy. The types of physical systems to be studied are of a multilayer variety whose building block is usually composed of two materials having different band gaps. This difference in band gaps can lead to the confinement of carriers in one of the two materials (that is, the carriers can become confined to a quantum well). With modulation spectroscopy, the derivative of the absorptivity or reflectivity with respect to some parameter is evaluated. This spectroscopy is sensitive to critical-point transitions in the Brillouin zone, while the resulting spectrum has sharp derivative-like features and a little, if any, featureless background. © 1992, Academic Press, Inc.