Browsing by Author "Tretyak, O"

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A computational method for energy level spin splitting simulation in InAs/GaAs semiconductor quantum dots
(2002-05-01)
Li, YM
;
Voskoboynikov, O
;
Lee, CP
;
Sze, SM
;
Tretyak, O
An impact of the spin-orbit interaction on the electron quantum confinement is considered theoretically for narrow gap semiconductor cylindrical quantum dots. To study the phenomena for InAs quantum dot embedded into GaAs semiconductor matrix, the effective one electronic band Hamiltonian, the energy position dependent electron effective mass approximation, and the spin-dependent Ben Daniel-Duke boundary conditions axe considered, formulated and solved numerically. To solve the nonlinear Schrodinger equation, we propose a nonlinear iterative algorithm. This calculation algorithm not only converges for all simulation cases but also has a good convergent rate. With the developed quantum dot simulator, we study the effect of the spin-orbit interaction for narrow gap InAs/GaAs semiconductor cylindrical quantum dots. From the numerical calculations, it has been observed that the spin-orbit interaction leads to a sizeable spin-splitting of the electron energy states with nonzero angular momentum. Numerical evidence is presented to show the splitting result is strongly dependent on the quantum dot size.
Effect of shape and size on electron transition energies of InAs semiconductor quantum dots
(2002-04-01)
Li, YM
;
Voskoboynikov, O
;
Lee, CP
;
Sze, SM
;
Tretyak, O
We present a theoretical study of the electron energy states in three-dimensional narrow gap semiconductor quantum (Jots with different shapes under an external magnetic field. The problem is solved by using the effective one-electronic-band Hamiltonian, the energy- and position-dependent electron effective mass approximation and the Ben Daniel-Duke boundary condition. We investigate small InAs/GaAs quantum dots with disk, lenticular, and conical shapes. Electron energy dependence on volume is expressed as V-gamma where the exponent gamma depends on the dot shapes and can vary over a wide range. The most stable against the dot size deviations (among dots of the same base radius) is the energy spectra of the conical dots. In addition, this type of dot also has the weakest diamagnetic shift. Contrarily, quantum dots with cylindrical shapes show a wide deviation in energy and a relatively strong diamagnetic shift.
Electron energy state dependence on the shape and size of semiconductor quantum dots
(2001-12-15)
Li, YM
;
Voskoboynikov, O
;
Lee, CP
;
Sze, SM
;
Tretyak, O
In this article we present a unified model for studying the effect of the sizes and shapes of small semiconductor quantum dots on the electron and hole energy states. We solved the three-dimensional effective one band Schrodinger equation for semiconductor quantum dots with disk, lenticular, and conical shapes. For small InAs/GaAs quantum dots we found a substantial difference in the ground state and first excited state electron energies for dots with the same volume but different shapes. Electron energy dependence on volume is found to be quite different from the commonly quoted V-2/3. The exponent can vary over a wide range and depends on the dot shapes. (C) 2001 American Institute of Physics.
Electron energy state spin-splitting in 3D cylindrical semiconductor quantum dots
(2002-08-01)
Li, Y
;
Voskoboynikov
;
Lee, CP
;
Sze, SM
;
Tretyak, O
In this article we study the impact of the spin-orbit interaction on the electron quantum confinement for narrow gap semiconductor quantum dots. The model formulation includes: (1) the effective one-band Hamiltonian approximation; (2) the position- and energy-dependent quasi-particle effective mass approximation; (3) the finite hard wall confinement potential; and (4) the spin-dependent Ben Daniel-Duke boundary conditions. The Hartree-Fock approximation is also utilized for evaluating the characteristics of a two-electron quantum dot system. In our calculation, we describe the spin-orbit interaction which comes from both the spin-dependent boundary conditions and the Rashba term (for two-electron quantum dot system). It can significantly modify the electron energy spectrum for InAs semiconductor quantum dots built in the GaAs matrix. The energy state spin-splitting is strongly dependent on the dot size and reaches an experimentally measurable magnitude for relatively small dots. In addition, we have found the Coulomb interaction and the spin-splitting are suppressed in quantum dots with small height.
Magnetic properties of parabolic quantum dots in the presence of the spin-orbit interaction
(2003-11-01)
Voskoboynikov, O
;
Bauga, O
;
Lee, CP
;
Tretyak, O
;
交大名義發表
We present a theoretical study of the effect of the spin-orbit interaction on the electron magnetization and magnetic susceptibility of small semiconductor quantum dots. Those characteristics demonstrate quite interesting behavior at low temperature. The abrupt changes of the magnetization and susceptibility at low magnetic fields are attributed to the alternative crossing between the spin-split electron levels in the energy spectrum, essentially due to the spin-orbit interaction (an analog of the general Paschen-Back effect). Detailed calculation using parameters of InAs semiconductor quantum dot demonstrates an enhancement of paramagnetism of the dots. There is an additional possibility to control the effect by external electric fields or the dot design. (C) 2003 American Institute of Physics.
Spin-dependent electron scattering from quantum dots and antidots in two-dimensional channels
(2002-01-01)
Voskoboynikov, O
;
Huang, HC
;
Lee, CP
;
Tretyak, O
;
電子工程學系及電子研究所
Electron elastic scattering from two-dimensional circular quantum dots (antidots) when the spin-orbit interaction plays an important role is studied theoretically. The investigation is based on the effective one electronic band Hamiltonian and the spin-dependent boundary conditions. It was found a large left-right spin-dependent asymmetry in the scattering cross section for two-dimensional electrons. In a case of GaAs InAs antidots the asymmetry reaches similar to 10% for back-scattered electrons. (C) 2002 Elsevier Science B.V. All rights reserved.
Spin-orbit energy state splitting in semiconductor cylindrical and spherical quantum dots
(2001-07-01)
Voskoboynikov, O
;
Lee, CP
;
Tretyak, O
;
交大名義發表
;
National Chiao Tung University
We present a theoretical study of the spin-orbit interaction impact on electron energy states in small cylindrical and spherical quantum dots. The investigation is based on the effective one-electronic band Hamiltonian and the spin dependent boundary conditions. It has been demonstrated that the spin-orbit interaction can significantly modify the energy spectrum of InAs and InSb quantum dots. The splitting can provide a situation where only the lowest spin split energy states are bound in the dot. A reasonable agreement was found with data from more sophisticated theoretical models for the spherical quantum dots which is available in the literature.
Spin-orbit interaction and energy states in semiconductor quantum dots
(2001-05-01)
Voskoboynikov, O
;
Lee, CP
;
Tretyak, O
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We present a theoretical study of the impact of the spin-orbit interaction on electron energy states in small cylindrical quantum dots. In our calculations, we use the effective one electronic band Hamiltonian and the spin dependent boundary conditions. It has been found that the spin-orbit interaction can modify the energy spectrum of narrow gap semiconductor quantum dots. The modification consists of the energy state spin splitting that strongly depends on the dot size. The spin splitting demonstrates a non-monotonic dependence on the dot size and can provide a situation when only the lower spin split states with angular quantum number l =1 are bound in the dot. (C) 2001 Elsevier Science B.V. All rights reserved.
Spin-polarized electronic current in resonant tunneling heterostructures
(2000-01-01)
Voskoboynikov, A
;
Lin, SS
;
Lee, CP
;
Tretyak, O
;
交大名義發表
The spin-dependent tunneling phenomenon in symmetric and asymmetric resonant semiconductor heterostructures is employed in a theoretical study to investigate the output tunnel current polarization at zero magnetic field. A simple model of the resonant tunneling structures and a simple one-electron band approximation with spin-orbit interaction are used in this work. It is shown that asymmetry in the electron distribution at the electrode regions provides spin-polarized tunnel current. An approach to optimize this spin-dependent effect is explored theoretically. In asymmetric resonant tunneling structures, we estimate theoretically that the polarization can reach 40% with a moderate applied electric field. (C) 2000 American Institute of Physics. [S0021- 8979(00)09501-3].