Abstract:Using a variational procedure for a hydrogenic donor-impurity we have investigated the influence of an axial magnetic field and hydrostatic pressure in the binding energy and the impurity-related photoionization crosssection in 1D and 0D GaAs low dimensional systems. Our results are given as a function of the radius, the impurity position, the polarization of the photon, the applied magnetic field, the normalized photon energy, and the hydrostatic pressure. In order to describe the Γ-X mixing in the Ga 1−x Al … Show more
“…It is also noted that as the well length increases, the binding energy of the hydrogenic donor impurity tends towards a constant value of about 44.0 meV. This compares favorably with that found by Correa, et al [27]. That is, the binding energy is a nonmonotonic function of the well width and peaks at a relatively small width value.…”
In the present work, a theoretical study of the variation of the photoionization cross-section with the incident photon frequency and the axial position of a hydrogenic donor impurity in GaAs quantum well dot of square cross-section is carried out. In the calculation, a trial wave function in the effective mass approximation and a finite potential well is used. The wave function is constructed with an appropriate envelope wave function that satisfies the boundary conditions, i.e., the wave function vanishes at the boundary. A trial wave function is employed to calculate the total energy of the hydrogenic donor impurity in the ground state. The total energy is then minimized with respect to the variational parameter in the trial wave function to obtain the minimum energy. The minimized total energies are then used to determine the donor binding energies within the quantum dot. It is observed that for a quantum dot of constant cross-section, the binding energy increases with a decrease in dot length to a peak value; thereafter it decreases rapidly towards zero. The binding energies obtained are used to compute the photoionization cross-section of the hydrogenic donor impurity as a function of the incident photon frequency for different positions of the donor impurity. It is observed that the photoionization cross-sections rise steeply to their peaks from almost zero value then gradually decrease as the photon frequency increases until they become almost constant for very high photon frequencies. The photoionization cross-section peak is much higher for the hydrogenic donor impurity located closest to the centre of the quantum well dot than for donor impurity located farther away from the dot centre. This indicates that the photoionization cross-section is sensitive to the location of the donor impurity in the quantum dot and to the incident photon frequency.
“…It is also noted that as the well length increases, the binding energy of the hydrogenic donor impurity tends towards a constant value of about 44.0 meV. This compares favorably with that found by Correa, et al [27]. That is, the binding energy is a nonmonotonic function of the well width and peaks at a relatively small width value.…”
In the present work, a theoretical study of the variation of the photoionization cross-section with the incident photon frequency and the axial position of a hydrogenic donor impurity in GaAs quantum well dot of square cross-section is carried out. In the calculation, a trial wave function in the effective mass approximation and a finite potential well is used. The wave function is constructed with an appropriate envelope wave function that satisfies the boundary conditions, i.e., the wave function vanishes at the boundary. A trial wave function is employed to calculate the total energy of the hydrogenic donor impurity in the ground state. The total energy is then minimized with respect to the variational parameter in the trial wave function to obtain the minimum energy. The minimized total energies are then used to determine the donor binding energies within the quantum dot. It is observed that for a quantum dot of constant cross-section, the binding energy increases with a decrease in dot length to a peak value; thereafter it decreases rapidly towards zero. The binding energies obtained are used to compute the photoionization cross-section of the hydrogenic donor impurity as a function of the incident photon frequency for different positions of the donor impurity. It is observed that the photoionization cross-sections rise steeply to their peaks from almost zero value then gradually decrease as the photon frequency increases until they become almost constant for very high photon frequencies. The photoionization cross-section peak is much higher for the hydrogenic donor impurity located closest to the centre of the quantum well dot than for donor impurity located farther away from the dot centre. This indicates that the photoionization cross-section is sensitive to the location of the donor impurity in the quantum dot and to the incident photon frequency.
“…7 Sahin 8 has studied the photoionization cross the section of the hydrogenic impurity and intersubband energy level transitions which depend on the size of the quantum well. The binding energy and the dependence of the photoionization cross section on the heterostructure sizes, confining-potential barrier height, applied hydrostatic pressure and magnetic field in the growth direction were investigated by Correa et al 9 who found that the cross section shifts to higher energies when the hydrostatic pressure is increased. Further, Kasapoglu et al 10 have investigated the photoionization cross section in a GaAs/GaAlAs quantum well wire and found that the cross section is affected by the wire size and by the alloy of the barrier.…”
The ground state and low lying-excited state energies of a hydrogenic impurity located at the centre of a strained Zn 1−x Cd x Se/ZnSe quantum dot have been computed as a function of dot radius with various Cd content. Calculations have been performed using Bessel function as an orthonormal basis for different confinement potentials of barrier height considering the internal electric field induced by the spontaneous and piezoelectric polarizations. Photoionization cross section of hydrogenic impurity in a quantum dot is investigated. We study the oscillator strengths, the linear and third-order nonlinear optical absorption coefficients as a function of incident photon energy for 1s-1p and 1p-1d transitions. It is found that the optical properties in the strained ZnCdSe/ZnSe quantum dot are strongly affected by the incident photon energy, the confinement potentials and the dot radii and the optical transition energy which depends on the dot radii and the barrier height and tunes the resonant frequency.
“…Works regarding the effects of the hydrostatic pressure on shallow donor impurities have been carried out by Gonzalez et al, Correa and collaborators, and Kasapoglu et al [2][3][4] in quantum well (QW) systems. Morales et al studied the polarization caused by an applied electric field on donor impurities [5] and Morales and Kasapoglu have reported the combined effects of the hydrostatic pressure and electric field on shallow donor impurities in double QW [6,7].…”
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