Dielectric and Magnetic Properties of Superlattices.
Abstract
Available from UMI in association with The British Library. Requires signed TDF. The coupling of the classical electromagnetic field with the phonon field in semiconductor superlattices is studied. It is shown from the exact equations for transverse electromagnetic waves propagating in an infinitely extended superlattice that, in the longwavelength limit, the superlattice has the optical properties of an unconventional uniaxial medium, with the optic axis normal to the layer planes. This result is used to derive the frequency dependence of the superlattice's effective dielectrictensor components. By using the effective medium description, the dispersion relation for bulk phononpolaritons is derived along with the dispersion relation for surface polaritons at the interface of a superlattice and an isotropic, homogeneous medium. The effectivemedium description is then used to interpret farinfrared normal incidence reflectivity measurements from a GaAs/Al_{rm x}Ga_{rm 1x} As multiquantum well (MQW) structure. A least squares fit of theory to experimental data gives values for the reststrahlregion parameters of the GaAs and Al _{rm x}Ga _{rm 1x}As layers. Calculations are then performed for the theory of farinfrared attenuated total reflection (ATR) from semiconductor MQW's. Features in the ATR curves for p polarized incident light are identified as corresponding to surface or guidedwave polaritons. Curves for spolarization show only guidedwaves. Comparisons are given of theoretical ATR curves with recently obtained experimental curves. The coupling of electromagnetic waves with spin waves in magnetic superlattices is also considered. The dispersion relation for bulk TE and TM magneticpolaritons are derived and from the full dispersion relation for TE modes, a longwavelength description of the magnetic superlattice is given. An effective magnetic permeability tensor for the superlattice is derived and these results are used to obtain longwavelength bulk dispersion relations. Green functions for the magnetic superlattice are derived and possible applications for them are discussed.
 Publication:

Ph.D. Thesis
 Pub Date:
 June 1988
 Bibcode:
 1988PhDT........46R
 Keywords:

 Physics: Electricity and Magnetism