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Öğe Binding energy of a hydrogenic impurity in a coaxial quantum wire with an insulator layer(Academic Press Ltd- Elsevier Science Ltd, 2017) Kes, H.; Bilekkaya, A.; Aktas, S.; Okan, S. E.The electronic properties of a coaxial cylindrical quantum well-barrier system constituted about an central insulating wire were determined under an external electric field. The model wire, inside to outside, was considered to be layered as AlAs/GaAs/Alx1Ga1-xAs/GaAs/Alx2Ga1-x2As. Within the framework of the effective mass approximation, the binding energy of a hydrogenic impurity is calculated by using the combination of the fourth-order Runge-Kutta method and variational approaches. The binding energy exhibits sharp changes depending on the impurity position and the geometrical parameters of the structure such as the well widths of the GaAs wires and the height and thickness of the barrier constituted by Alx1Ga1-x1 As. The binding energy of the electron was found to be independent from the impurity position for the specific widths of the well wires. Also, the barrier properties appeared as very effective parameters in controlling the probability distribution of the electron. (C) 2017 Elsevier Ltd. All rights reserved.Öğe Electric and magnetic field effects on the binding energy of a hydrogenic impurity in quantum well wires with different shapes(Academic Press Ltd- Elsevier Science Ltd, 2008) Bilekkaya, A.; Aktas, S.; Okan, S. E.; Boz, F. K.In this work, we directly calculate the ground state energies for an electron in quantum well wires (QWWs) with different shapes in the presence of applied electric and magnetic fields using the finite difference method. Then, we study the ground state binding energy of a hydrogenic impurity with a variational approach. We obtain the binding energy for QWWs consisting of the combinations of square and parabolic well potential. Our results indicate that the impurity binding energy depends strongly on the structural confinement and also, on the applied electric and magnetic field. (c) 2008 Elsevier Ltd. All rights reserved.Öğe Electron transmission in symmetric and asymmetric double-barrier structures controlled by laser fields(Academic Press Ltd- Elsevier Science Ltd, 2015) Aktas, S.; Bilekkaya, A.; Boz, F. K.; Okan, S. E.The potential profiles of symmetric and asymmetric rectangular double-barrier structures made of (Ga, Al)As/GaAs and the transmission coefficient of an electron in these systems have been investigated under intense laser field. The results show that the field alters the potential profile, and the transmission coefficient can thus be controlled. The transmission at the first resonance energy for the symmetric structure is higher than that of the asymmetric structure. Therefore, the symmetric design is feasible. The properties exhibited in this work may establish guidance to device applications. (C) 2015 Elsevier Ltd. All rights reserved.Öğe The electronic properties of a coaxial square GaAs/AlxGa1-xAs quantum well wire in an electric field(Elsevier Science Bv, 2009) Aktas, S.; Boz, F. K.; Bilekkaya, A.; Okan, S. E.The binding energy of a hydrogenic impurity in a coaxial square quantum well wire (QWW) system is investigated as a function of the barrier thickness for two different impurity positions under the electric fields. Within the effective mass approximation, the ground state energy in the presence of an external electric field applied perpendicular to the symmetry axis of the wire system is calculated using the finite difference method. Then, the ground state binding energy of a hydrogenic impurity is found employing a variational method. It is found that the binding energy in critical barrier thickness shows an increase or decrease depending on the impurity position and electric field strength. (C) 2009 Elsevier B.V. All rights reserved.Öğe The energy spectrum for an electron in quantum well wires with different shapes under the electric and magnetic fields(Elsevier Science Bv, 2008) Aktas, S.; Bilekkaya, A.; Okan, S. E.The ground-state energies and wave functions for an electron in quantum well-wires (QWWs) with different shapes under the electric and magnetic fields are directly calculated using the finite difference method. It is shown that the method is able to calculate all energy states for any given QWW shape. Then, the ground-state binding energy of a hydrogenic impurity is found employing a variational method. The reliability of the results is tested against previous studies. The binding energy for QWWs consisting of the combinations of square and triangular well potential is obtained. (C) 2008 Elsevier B.V. All rights reserved.Öğe Investigation of the coupling asymmetries at double-slit interference experiments(Iop Publishing Ltd, 2010) Mese, A. I.; Bilekkaya, A.; Arslan, S.; Aktas, S.; Siddiki, A.Double-slit experiments inferring the phase and the amplitude of the transmission coefficient performed at quantum dots (QDs), in the Coulomb blockade regime, present anomalies at the phase changes depending on the number of electrons confined. This phase change cannot be explained if one neglects the electron-electron interactions. Here, we present our numerical results, which simulate the real sample geometry by solving the Poisson equation in 3D. The screened potential profile is used to obtain energy eigenstates and eigenvalues of the QD. We find that, certain energy levels are coupled to the leads stronger compared to others. Our results give strong support to the phenomenological models in the literature describing the charging of a QD and the abrupt phase changes.Öğe The multilayered spherical quantum dot under a magnetic field(Elsevier Science Bv, 2010) Boz, F. K.; AktasA, S.; Bilekkaya, A.; Okan, S. E.The binding energy of an impurity located at the center of multilayered spherical quantum dot (MSQD) is reported as a function of the dot and barrier thickness for different alloy compositions under the influence of a magnetic field. Within the effective mass approximation, the binding energy has been calculated using the fourth order Runge-Kutta method without magnetic field. A variational approach has been employed if a magnetic field is present. The binding energy in MSQD with equal dot and barrier thickness is calculated. It is shown that the binding energy in MSQD differs from that of a single quantum dot. Also, the geometry is dominant on the binding energy for thin MSQDs, but the magnetic field becomes more effective for thick MSQDs. (C) 2010 Elsevier B.V. All rights reserved.
