THEORY OF OPTICAL PROPERTIES OF QUANTUM WELLS, WIRES AND DOTS

摘要

The electronic states in quantum confined semiconductor structures are reviewed. The corresponding quantization and the resulting sub-bands are discussed as well as the conditions under which these structures can be considered as quasi-two-, one-, or zero-dimensional. The density-of-states for these lower dimensional structures are derived. Because of rapid dephasing and relaxation processes density matrices - or on a more advanced level non-equilibrium Green functions- are most appropriate for the descriptions of the electrons participating in the optical transitions. The equations of motion for the single-particle density matrices - often called the semiconductor Bloch equations- form the appropriate theoretical framework for calculating the optical properties. They allow to calculate not only linear optical properties with and without external static fields, but also the nonlinear and time-resolved optical responses. We stress the changes which arise compared to bulk materials. The review is largely based on the chapter "Theoretical Concepts" by the author in Semiconductor Quantum Structures, Subvolume C Optical Properties I, ed. C. Klingshirn, Landoldt-Boernstein Vol. 34, Springer, Berlin 2001, p. 6.