Researches On Electron States, Phonon States And Electron-Phonon Interactions In Semiconductor Low-Dimensional Quantum Structures

In the last several decades, the semiconductor low-dimensional quantum structures have become one of frontier research topics in condensed matter physics and material science as they exhibit some novel physical properties and potential application values. Simultaneously, the rapid advances and maturing in the ul-trathin growth, such as molecular beam epitaxy, and nanoscale lithography techniques have made it possible to fabricate various nano-devices. In the present thesis, electronic states, phonon modes and electron-phonon interactions in semiconductor superlattice ( SL ) with structural defects which is one type of specific low-dimensional quantum structure are deeply investigated, and some useful results are obtained. It is expected to be helpful theoretically for the design and manufacture of quantum devices.Within the framework of effective-mass approximation, the properties of the localized electronic states in a N-layer SL with structural defects at finite magnetic fields are investigated by utilizing the transfer matrix and effective barrier-height methods. When the mismatch of electron effective mass in different constituent layer is considered, an external magnetic field will lead to the appearance of magneto-coupling effect. Our numerical results show that the magneto-coupling effect brings about not only quantization of localized electron levels but also the strong dependence of the localized levels and degree on Landau indices and magnetic fields, especially for the localized levels in higher energy region. In addition, we demonstrate in detail the correlations between the localized electronic states inside the minigaps of the infinite SL with structural defect layer and the resonant transmission peaks in dips of the finite SL. A good coincidence between the localized states and transmission peaks is found, which provide a theoretical basis for experimental observation of the localized electronic states in SLs. As the N-layer SLs have been proved to be useful to improve performance of multi-quantum-well lasers and infrared photodetectors, these results could help to model the basic phenomena underlying device operation.Using a transfer matrix method, we study the property of the interface optical-phonon modes (IOPMs) in a finite semiconductor SL with structural defect layer in the dielectric continuum approximation. In such a finite SL, the evolution of...