Binding Energy Of Impurity Research Articles

The External Electric and Magnetic Fields Effect on Binding Energy of Hydrogenic Donor Impurity in a InGaAsP/InP Core–Shell Quantum Dot

The External Electric and Magnetic Fields Effect on Binding Energy of Hydrogenic Donor Impurity in a InGaAsP/InP Core–Shell Quantum Dot

Pressure effect on the diamagnetic susceptibility of donor in HgS and GaAs cylindrical quantum dot

The binding energy and diamagnetic susceptibility of shallow hydrogenic impurity in cylindrical quantum dot is calculated using a variational approach within the effective mass approximation, as a function of dot size when the static pressure and the magnetic field are applied simultaneously. We describe the quantum confinement by an infinite deep potential; the numerical calculations are performed for HgS, which is a narrow gap, and GaAs, a large gap semiconductor. The results show that the diamagnetic susceptibility increases with the reduction in dot sizes and decreases when the hydrostatic pressure increases. We have shown that diamagnetic susceptibility strongly depends on size of the nanostructure and decreases with increasing size of the quantum dot and tends toward the limit of the bulk (−1, 1 a.u.) (increase in diamagnetic susceptibility in absolute value). We have found that the displacement of the impurity from the center of the quantum dot to the edge causes a decrease in the diamagnetic susceptibility. The absolute value of diamagnetic susceptibility of donors in GaAs is lower than in HgS.

Magnetic properties of GaAs parabolic quantum dot in the presence of donor impurity under the influence of external tilted electric and magnetic fields

The dependence of the magnetization and magnetic susceptibility of donor impurity in parabolic GaAs (Gallium Arsenide) quantum dot has been investigated, at finite temperature under the influence of external tilted electric and magnetic fields. Based on the effective mass approximation, the Hamiltonian of an electron confined in a parabolic quantum dot in the presence of donor impurity which is presented in electric and magnetic fields has been solved by employing the numerical diagonalization method of the Hamiltonian matrix. All the energy matrix elements have been obtained in analytical form. We have shown the variations of the statistical energy and binding energy of donor impurity with the electric and magnetic field strengths and tilt electric field angle. The computed results show that the electrical field can tune the magnetic properties of the QD GaAs medium by flipping the sign of its magnetic susceptibility from diamagnetic (χ < 0) to paramagnetic (χ > 0).

Binding energies and photoionization cross-sections of donor and acceptor impurities in inverted core/shell ellipsoidal quantum dots: Effects of magnetic field, ellipsoid anisotropy and impurity position

Within the framework of the effective-mass approximation and by using a variational and perturbation approach, the binding energies and photoionization cross-sections of donor and acceptor impurities in an inverted core/shell ellipsoidal spherical quantum dot under an applied magnetic field have been studied. We have calculated the binding energies of both donor and acceptor impurities as a function of the core and shell sizes and shapes with different impurity positions under the applied magnetic field. In addition, the corresponding photoionization cross-section is calculated. Our results show that the binding energy of the acceptor impurity is larger than that of the donor impurity, and both of them with different impurity positions and quantum ellipsoid anisotropies will exhibit a nonmonotonic change. The peak value of the photoionization cross-section will reach a maximum with the increasing ratio R1/R2. It is found that the applied magnetic field can be an effective means of enhancing the photoionization cross-section of an impurity state in such core/shell quantum dot system.

Anisotropy dependence of the optical response in an impurity doped quantum dot under intense laser field

In the present work, we are interested in calculating anisotropy dependence of the optical response in an ellipsoidal quantum dot with a hydrogenic impurity in the presence of high-frequency intense laser field within the framework of the effective mass approximation. The effects of the anisotropy of the system and laser field intensity on the energy levels and the respective impurity binding energies are calculated. It is shown that the electrostatic interaction between the electron and the impurity atom becomes the weakest when the structure has a spherical symmetry and in contrast to the 1s-like state, the binding energy of the 2pz-like state increases with the laser field intensity for all values of the anisotropy parameter considered. The results show that the anisotropy degree plays a fundamental role in determining the optical response of the ellipsoidal quantum dot.

Effect of electric and magnetic field on impurity binding energy in InGaAsP/InP quantum ring

The ground state binding energy of hydrogenic donor impurity is calculated using the plane wave basis method in InGaAsP/InP quantum ring under applied electric and magnetic fields. The results show that the binding energy is nonlinear function of ring height and outer radius. The binding energy has a maximum near the center of radial or axial direction. The external electric field changes the probability distribution of electron, and then the difference of binding energies for impurity located at symmetrical positions increases. The binding energy increases with the increase of magnetic field and the effect of magnetic field is more obvious along the direction of magnetic field.

Screened shallow impurity properties of quantum well heterosystems with high-κ dielectric barrier environment

The effect of high-κ dielectric mismatch on the impurity states screened by free electron gas is investigated theoretically in high-κ dielectric barrier/quantum well/high-κ dielectric barrier (hh-κ) and low-κ dielectric barrier/quantum well/high-κ dielectric barrier (lh-κ) types of quasi two-dimensional (Q2D) heterostructures. A restriction of the characteristic long-range nature of the impurity Q2D screened interaction due to the high-κ dielectric mismatch has been revealed here - atypical of the Q2D dielectrically homogeneous systems. Accordingly, for the hh-κ type heterostructure, an impurity screened interaction potential at moderately large (relative to the quantum well width values) in-plane distances behaves as the Q2D Debye-Hückel potential, while at rather large distances falls off on the background of the high-κ dielectric constant of the barrier medium. The screened impurity ground state energy in the framework of the Q2D Debye-Hückel potential has been investigated variationally for the first time. A role of high-κ dielectric mismatch is exposed when comparing the results for the discussed heterostructures based on the realistic InSb/HfO2 interface. The characteristic ranges where the quantum confinement effect, enhancing the Coulomb interaction, balances the joint weakening influence of the impurity screening and high-κ dielectric mismatch effects are revealed. The received admissible values of the in-plane density/temperature ratio parameter for the hh-κ type heterostructure typically refer to non-degenerate electron gas while for the lh-κ type both electron gas statistics are significant. Due to the high-κ dielectric mismatch a binding energy sufficient decline with reducing of the quantum well width has been established. In the hh-κ type heterostructure an impurity binding is quite sizable at the wide quantum wells (d ∼8 ÷ 10 nm). Meanwhile, for the lh-κ-type heterostructure, an impurity binding energy is enough large (∼10 meV) in both wide and narrow quantum well cases.

Energy of Hydrogenic Impurities in Spherical Quantum Dot

The present study has provided a new method for calculating the ground state and binding energy. The ground state and binding energy of a hydrogenic impurity in spherical quantum dot calculate by using the Feynman path integral. Hydrogenic impurity located at the center of quantum dot. The framework is center of the effective-mass theory.

Hydrogenic donor impurities in -doped cylindrical quantum dots under intense laser field

A theoretical study of the effects of non-resonant intense laser field on the donor impurity binding energy in a cylindrical quantum dot with -doped axial potential is performed in the framework of the effective mass approximation. The obtained results indicate that, 2D impurity concentration and intense laser field intensity have a significant effect on the impurity binding energy and energy levels of electrons in the cylindrical quantum dots with -type axial potential.

Interband and intersubband optical transition energies in a Ga0.7In0.3N/GaN quantum dot

Binding energies of a hydrogenic donor impurity and an exciton are investigated in a Ga0.7In0.3N/GaN parabolic quantum dot taking into consideration of spatial confinement effects and the magnetic and electric fields. The strain effects and the built-in internal fields which are related to the piezoelectricity and spontaneous polarization are inserted in the Hamiltonian of the system. Numerical calculations on electronic and optical properties are performed using variational formulism and the density matrix approach. The diamagnetic shift is obtained taking into the account the geometrical confinement effect of the dot. The magnetic and electric fields dependent interband and intraband optical transition energies are obtained in the strong and weak confinement effects. Their corresponding oscillator strengths as functions of magnetic and electric fields are investigated. The optical absorption coefficients due to intersubband and interband transitions with the photon energy are obtained. The results show that the energy shift is much influenced with the inclusion of external perturbations. Specifically, the optical absorption peak undergoes a redshift with the application of electric field whereas it suffers a blue shift when the magnetic field is applied. The results will be helpful for the experimental works on fabricating optical devices such as photodetectors and laser amplifiers using nitride based wide band gap semiconductors.

The Binding Energy of Impurities in the Asymmetrical Semi-Exponential Quantum Wells

Within the framework of effective-mass and envelope wave function approach, using a variational method, we have investigated the binding energy of shallow-donor impurities in an asymmetrical semi-exponential quantum wells (ASEQW). The obtained numerical results show that the structure parameters (σ and, V0) lead to significant changes in the impurity binding energy. Furthermore, these results show that the hydrogenic donor impurity binding energy may be increased or decreased as a function of the impurity position in quantum well.

Morse quantum well modulated by nonresonant intense laser field: Binding energy and optical absorption related to shallow donor impurities

Binding energies of the lowest two s-symmetric impurity states and linear, third order nonlinear, and total optical absorption coefficients corresponding to the 1s → 2s transitions for electrons in a Morse quantum well are investigated. Influence of a non-resonant intense laser field is considered for different values of the structure parameter, impurity position, and laser field intensity. In order to find the eigenvalues and eigenfunctions of the unbound electron confined within the Morse quantum well under the intense laser field, the time independent Schrödinger equation is solved by using the effective mass and parabolic band approximations. The impurity binding energy is determined by means of a variational procedure, using hydrogen-like trial wave functions, and the optical response is treated with the use of a two-level approach in the density matrix expansion. Our results show that it is possible to design suitable devices described by a Morse-like confinement pattern in the desired wavelength by changing the mentioned parameters.

Role of a uniform magnetic field on the energy spectrum of a single donor in a core/shell spherical quantum dot

Using the variational approach within the framework of the effective-mass approximation (EMA), the binding energy of a centred hydrogenic donor impurity in a CdSe/ZnTe core/shell spherical quantum dot (CSSQD) in the presence of an external magnetic field was investigated. In this model, we have taken into account the effect of the radial dependence of the dielectric constant and of the electron effective mass. Our numerical results show a remarkable influence of the nanodot spatial parameters and of the external magnetic field strength on the shallow donor binding energy.

Influence of image charge effect on the binding energy of hydrogen-like donor impurity in a near-surface quantum well under transverse electric field

We present a systematic theoretical study of the influence of image charges on the spectrum of a shallow donor impurity located anywhere in a near-surface quantum well under the electric field applied along the growth direction of the system. We calculate the binding energies of the ground and excited donor impurity states in the effective-mass approximation using the variational method for various values of the quantum well width, electric field strength, and donor positions within the well. Theoretical results indicate that the role of image charges is especially important for small widths of a quantum well. In contrast to the ground state, the influence of image charges on the binding energy of excited states is significant only at small values of the electric field. Therefore such fields can serve as a means to control the transition energies between ground and first excited states.

Hydrogenic donor in a CdSe/CdS quantum dot: Effect of electric field strength, nanodot shape and dielectric environment on the energy spectrum

The impact of an external electric field on the binding energy of a single donor impurity was examined within the effective-mass approach by deploying a variational calculation. The discontinuity of the permittivity, ɛr, and of the particle effective mass, mi*r, at the nanosystem boundaries was considered. Using the image charge approach, the impact of the surrounding medium on the shallow donor energy spectrum was also taken into account. Our theoretical investigation shows that, for zero electric field and when the shell thickness is taken constant, the increase of the core material size leads to decrease the single donor correlation energy. Further, for a fixed core material size the energy decreases quickly when the shell thickness moves from 0 to 1 nm, while it decreases very slowly when the shell thickness is ranged between 1 nm and 4 nm. On the other hand, we have established that when we turn on an external electric field, the probability density of confined particles tends to move towards the nanodot border which naturally shifts the energy spectrum to lower energies (redshift). It was also obtained that the donor Stark shift depends not only on the nanodot size, but also on the surrounding medium.

The impacts of electric and magnetic field on the binding energy of hydrogenic donor impurity in a InGaAsP/InP ring-shaped quantum well wire

The ground state binding energy of a hydrogenic donor impurity in a InGaAsP/InP ring-shaped quantum well wire is calculated via the plane wave basis method. It is shown that the donor binding energy is strongly dependent on the geometry, impurity position, axial electric field and transverse magnetic field. In particular, the impacts on the binding energy due to axial electric field and transverse magnetic field can mutually compensate.

Interplay between normal and abnormal stark shift according to the quantum dot spherical core/shell size ratio

ABSTRACTThe effect of an applied external electric field on the binding energy of a donor impurity confined in a core/shell quantum dot is investigated taking into account the polarisation, self-polarisation contributions and the core/shell sizes. Calculations are performed in the framework of the effective mass approximation and using the Ritz's variational method. We show competition between the electric field and the polarisation. The advantage of our investigation is that it shows an interplay between a normal and an abnormal stark shift for certain regions characterised by typical core/shell sizes ratio. The dielectric mismatch effect due to the external medium dielectric constant has revealed an increasing of the binding energies.

Effect of conduction band non-parabolicity on bound polaron fundamental state in GaN/InN core shell quantum dots

In this paper, we present a theoretical investigation on the polaronic, impurity position and quantum confinement effects on the ground state binding energy of single dopant confined in cubic GaN/InN core/shell quantum dots. Within the framework of the effective mass and non-parabolic approaches, the Schrödinger equation is numerically solved by using the Ritz variational method. The polaronic corrections are included via the renormalization of the effective mass and a phonon-modified electron-impurity Coulombic interaction. It is found that the influence of both electron-phonon interaction and the band non-parabolicity result in the reduction of the ground state binding energy. The inclusion of the non-parabolicity leads to stronger decrease of the magnitude of the impurity binding energy. This points at the importance of including such element for an appropriate quantitative description of the spectrum of coupled electron-donor-impurity systems in nitride core/shell quantum dots.

Influence of polarization and self-polarization charges on impurity binding energy in spherical quantum dot with parabolic confinement

We present a general formulation of the ground state binding energy of a shallow hydrogenic impurity in spherical quantum dot with parabolic confinement, considering the effects of polarization and self energy. The variational approach within the effective mass approximation is employed here. The binding energy of an on-center impurity is computed for a GaAs/AlxGa1−xAs quantum dot as a function of the dot size with the dot barrier as parameter. The influence of polarization and self energy are also treated separately. Results indicate that the binding energy increases due to the presence of polarization charge, while decreases due to the self energy of the carrier. An overall enhancement in impurity binding energy, especially for small dots is noted.

External electric field effect on the binding energy of a hydrogenic donor impurity in InGaAsP/InP concentric double quantum rings

Within the framework of effective-mass envelope-function theory, the ground state binding energy of a hydrogenic donor impurity is calculated in the InGaAsP/InP concentric double quantum rings (CDQRs) using the plane wave method. The effects of geometry, impurity position, external electric field and alloy composition on binding energy are considered. It is shown that the peak value of the binding energy appears in two rings with large gap as the donor impurity moves along the radial direction. The binding energy reaches the peak value at the center of ring height when the donor impurity moves along the axial direction. The binding energy shows nonlinear variation with the increase of ring height. With the external electric field applied along the z-axis, the binding energy of the donor impurity located at z[Formula: see text] decreases while that located at z[Formula: see text] increases. In addition, the binding energy decreases with increasing Ga composition, but increases with the increasing As composition.