Theoretical Studies On Shallow Donor Impurity In A Spherical Parab Olic Quantum Dot With An Electric Field

In the past decades, the properties of low-dimensional semiconductor systemshave been the emerging subject in theoretical and applied physics. With the rapiddevelopment of advanced crystal-growth technology, quantum dot has been appliedextensively in various domains such as optoelectronics, nano-electronics, biomedicine,life sciences and quantum calculation, ect., molecular-beam expitaxy, metal-organicchemical-vapor deposition, ect. For the strong confinement to charge carriers in theselow dimensional strucures, many extremely di?erent physical and quite abundant opticalproperties were presented and investigated.It is reported that many new semiconductorphoto-electric and microelectronic quantum devices will be made from these lowdimensional structures in the future. Therefore, it is urgent for people to understandvarious physical properties of these structures. Research on the optical properties ofquantum dots is more convenient, especially in optical rectification , light absorption andthe refractive index. A large number of studies have shown that the low-dimensionalsemiconductor materials is very good, one of the non-linear optical materials. Withthe system of reduced size and dimension, and its nonlinear optical properties will bemore obvious and more extensive range of applications. Therefore, the low-dimensionalsemiconductor quantum dots of the nonlinear optical e?ect has become an important ele-ment in the research field of nonlinear optics. Composed by the five chapters of this thesis.In the first chapter, the general characters and applications of low dimensionalsemiconductor structures have been summarized brie?y.In the second chapter, we mainly study the impurity state of spherical quantumdots in the level by perturbation methods. Within the framework of e?ective-massapproximation, we discuss the levels of the impurity state, and analyze it to know thatthe confinement e?ect on the levels of the impurity state by perturbation methods. Thenwe study the the oscillator strength based on the computed energies and wave functions.The results show that the oscillator strength is strongly a?ected by the confinementstrength and the applied electric field.In the third chapter, we calculate the impurities e?ect on nonlinear optical absorptionand the refractive index coe?cient in semiconductor spherical quantum dots. By using the perturbation methods, we attempt to study the in?uence of radius of quantum dot,electric field, optical intensity and relaxation time on the linear and nonlinear opticalabsorption coe?cients as well as the linear and nonlinear refractive index changes.In the last chapter, summary of the paper and the main results are given; theshortage and further research are also mentioned.