Theoretical Studies On Raman Scattering In Semiconductor Quantum Dot System

With the rapid development of advanced crystal-growth technology, such as molecular-beam expitaxy, metal-organic chemical-vapor deposition, ect., various low dimensional semiconductor structures of different shape, such as quantum well, quantum wire and quantum dot can be grown. Due to the beneficial effects of strong confinement to current carriers in these low dimensional structures, lots of new optical phenomenon and effects have been investigated. It is reported that many new semiconductor photoelectric and microelectronic quantum devices will be made from these low dimensional structures in the future. Therefore, it is urgent for people to understand various physical properties of these structures. Raman scattering, for its convenience and no damage to the materials being measured, has become one of the most effective methods to provide direct information in the energy band structure and different physical properties of the low dimensional semiconductor systems. In the present dissertation, a theoretical study of the electron Raman scattering process has been presented in semiconductor quantum dot structures. The dissertation includes five chapters:In the first chapter, the general characters and applications of low dimensional semiconductor structures have been summarized briefly and a simple introduction to the current research of Raman scattering in low dimensional structures has been given.In the second chapter, electron Raman scattering is investigated in cylindrical quantum dot quantum well systems. Single parabolic conduction and valence bands are assumed. Different scattering configurations are discussed and the selection rules for the processes are also studied. Singularities in the spectra are found and interpreted.In the third chapter, theoretical calculations are carried out on the different cross section for the electron Raman scattering process associated with the bulk-like longitudinal optical and surface optical phonon modes in free standing spherical semiconductor quantum dots. Electron states are considered to be confined within the quantum dots. The selection rules for the Raman process are presented. Numerical results and discussions are presented for various radii, phonon quantum numbers, and for different materials.In the fourth chapter, a theoretical study of the Raman scattering associated with the bulk-like longitudinal optical and interface optical phonon modes is presented in special quantum dots heterostructures. Electrons are supposed to be confined in the dots. The Forhlich electron-phonon interaction is considered. The selection rules are presented. Numerical results and discussions are presented for various radii, phonon quantum numbers, and different Al content x for the barrier material (Al_xGa_1-xAs )In the last chapter, a brief summary of this paper, including the theories and the results, is given ; the shortage and further research are also mentioned.