Intraband Magneto-Optical Studies of Semiconductors in the Far Infrared. II

This chapter presents the intraband magneto-optical studies of semiconductors in the far infrared. The electronic energy levels of isolated impurities in semiconductors can frequently be described quite accurately in the effective mass approximation. A convenient parameter that characterizes the relative strength of the magnetic field is the ratio of free electron zero-point energy in the magnetic field to the effective Coulomb binding energy. The correspondence problem, the extension of the effective mass theory to include nonparabolicity and degenerate bands, the problem of central cell corrections, and the breakdown of the effective mass theory for deep impurities are examined. It is found that although donor impurities in InSb and GaAs have yielded the most precise information concerning hydrogenic energy levels in a magnetic field, a number of other materials have revealed similar, less detailed features. The interaction of free and bound carriers with collective excitations is elaborated. It is found that in this case, the energy separation between two excited electronic states is made equal to the phonon energy, while the initial state of the optical transition lies on a third level and terminates on the upper level of the pair of excited states.