Electromagnetic properties of semiconductors

The general features of electromagnetic wave propagation in semiconductors are described from the point of view of the classical phenomenological theory. Dispersion relations and the Lorentz-Drude models are used to explain general electromagnetic properties of semiconductors. The microscopic theory is developed and the optical excitation spectrum is related to interband transitions, exciton creation and other collective excitations. A symmetry analysis shows how selection rules can be established to single out the important transitions in the excitation spectrum. The importance of polariton states in the mechanism for absorption is illustrated, and the relation between transverse and longitudinal excitations is shown both in the classical and in the microscopic theory. (author)