Impurities Effects on Electronic, Thermal and Magnetic Properties of GaAs Quantum Dot/Ring Nanostructures رسالة دكتوراة

Abstract

In this thesis, the energy spectra of a tuned GaAs quantum dot/quantum ring (QD/QR) with parabolic-inverse squared potential and modified Gaussian confinement under an external magnetic field is studied. For this goal, the Schrödinger equation is analytically solved without and with considering the donor and acceptor impurities term and the energy eigenfunctions and eigenvalues are derived within the framework of effective-mass and parabolic band approximation. Also, the donor binding energy of the system has been theoretically investigated considering the various parameters. Moreover, the density of state has been studied in the QD/QR system characterized by varying magnetic fields, pressures, and impurity and computed over specified energy range using a comprehensive theoretical framework. Our analysis reveals significant variations in the density of state profiles corresponding to changes in these parameters, it provides remarkable insights into the electronic properties of materials. Based on the calculated energy spectra, the thermal functions of the system have been theoretically obtained. The partition function was calculated and then, the mean energy, free energy, specific heat, and entropy and variation of magnetic entropy of the tuned quantum dot/ring system with and without the impurity effect have been calculated; It is found that the presence of the impurity term causes the specific heat of the system to play a peaky structure. Also, it is observed that the temperature dependence of the magnetocaloric effect shows a pronounced maximum at specified temperatures. In addition, the computational results show that the impurity, temperature and magnetic field have a great influence on the magnetic characteristics of the system, the behavior of the magnetization and the magnetic susceptibility curves were studied. It is found that the magnetic susceptibility has both negative and positive values with changing the values of temperature and magnetic field strength. The results are offering a critical basis for future experimental researches and practical applications in material science and condensed matter physics.