Magnetotransport and Responses of Semiconductor Microstructures

Quantum theory of carrier transport in bulk semiconductors is considered through the use of Lei-Ting non-linear balance equation. The longitudinal magnetoresistivity due to impurity scatterers is examined in the linear limit, for both degenerate and non-degenerate statistics, and for all magnetic field strengths. In addition, the effect of various phonon scattering mechanisms is considered for both the linear and non-linear magnetoresistivity. Response phenomena of a periodically density modulated two-dimensional electron gas are examined. The magnetoplasma spectrum of such a system is shown to exhibit unusual oscillatory behavior. Such oscillations arise from the commensurability of the length scales of the system (period of modulation and cyclotron orbit radius at the Fermi level). A hydrodynamic theory of linear response is developed to examine the dielectric properties and the collective charge density oscillations of the system. In addition to the usual principal magnetoplasmon, a new mode appears as a result of the resonance drift of the cyclotron orbit center, periodic in 1/B. Both one -dimensional and two-dimensional modulated potentials are considered and the respective dielectric tensors and magnetoplasma modes are examined. Fast particle energy loss as a probe of the properties of a density modulated 2DEG in a magnetic field is analyzed. In the high velocity limit, the local plasmon spectrum makes two separate contributions to the energy loss for both the parallel and perpendicular cases. The principal plasmon mode makes a contribution to energy loss through vii the excitation of the hybrid 2D magnetoplasmon. The other plasmon mode contributes to the energy loss with features corresponding to Shubnikov-de Haas (SdH) oscillations subject to an amplitude envelope exhibiting commensurability oscillations. In the low-velocity limit the energy loss exhibits both SdH and commensurability oscillations. Inelastic light scattering from a density modulated 2DEG is also considered. The allowed transitions are indicated and the differential scattering cross-section is shown to give contribution from both the plasmon modes.