Superlattices Kinetic And Transport Theory

In this thesis, we investigate the dynamics properties of the superlattices under the influence of electric fields, and the coherent transport mechanism of the superlattices, i. e., dynamics of the two-band system in real space, and coherent transport properties of electrons in a Gaussian superlattice.In chapter 1, we introduce the evolution of semiconductor superlattices, the progress made in this field and the subject matter in this work.In chapter 2, we introduce the theoretical modes and others' work.In chapter 3. with the method of long-time averaged occupation probability(LAOP), we investigate the conditions of localization of an electron in the coupling two-band system under the action of ac and dc-ac fields. The values of LAOP can be calculated by Floquet theorem. We find with varying the electric field, the values of LAOP show some peaks, at which the electron can return repeatedly to the initial site or stay in the initial site forever. Interestingly, the electron can perform Rabi oscillation when we change the site energy of the two bands.In chapter 4, within the framework of the one-band effective-mass approximation, the single-electron two-dimensional Schrodinger equation is discretized. Then we investigate the electron transport in a scattering center connected to two perfectly ohmic leads with many transport modes. In the Kronig-Penney model with impurity, we discuss the effect of impurity upon the transport properties of the system; in a Gaussian superlattice, we find in some energy ranges, the electron can be nearly unscattered, and in other energy ranges, the electron can be nearly completely reflected.In chapter 5, we discuss the main conclusions and our expectation.