Binding Energy Of Impurity Research Articles

Magnetic field effect on the ground-state binding energy in InGaN/GaN parabolic QWW

Within the framework of the effective mass scheme, the ground-state binding energy of hydrogenic shallow-donor impurity in wurtzite (WZ) (In,Ga)N/GaN parabolic transversal-section quantum-well wire (PQWW) subjected to magnetic field is investigated. The finite-difference method within the quasi-one-dimensional effective potential model is used. A cylindrical QWW effective radius is introduced to describe the lateral confinement strength. The results show that: (i) the binding energy is the largest for the impurity located at a point corresponding to the largest electron probability density and (ii) it increases with increasing external magnetic field.

Effect of polarization charges on impurity binding energy in elliptical quantum wire

The binding energy of hydrogenic impurity located at the center of elliptical quantum wire using the effective mass approximation and an appropriate coordinate transformation is calculated for CdS/SiO2 structure. The effect of surface polarization charges due to impurity on the impurity binding energy is considered. The results clearly indicate that the binding energy depends not only on the polarization charges but also on the ellipticity constant.

Hydrostatic pressure and temperature dependence of dielectric mismatch effect on the impurity binding energy in a spherical quantum dot

Hydrostatic pressure, temperature and dielectric mismatch effects on the hydrogenic donor impurity binding energies of the low-lying states in a GaAs/AlxGa1−xAs spherical quantum dot is investigated by variational approach within the effective mass approximation. The impurity binding energy is computed as a function of dot size, hydrostatic pressure, temperature and dielectric mismatch effect. Our results show that the effect of hydrostatic pressure and dielectric mismatch effectively increases the impurity binding energy for narrower dots only. In contrast, the rise in temperature decreases the impurity binding energy for a given pressure and dot radius. Our results are in good agreement with the available literature values.

The finite element simulation for the shallow impurity in quantum dots

The finite element method (FEM) has been implemented in this paper to investigate the electronic state of shallow hydrogenic impurities in spherical GaAs (Al,As) quantum dots (SQDs) by taking into account the finite value of realistic potential barrier height. The nonlinear partial differential equations have been discretized by means of Galerkin's weighted residue method assuming a uniform partition and using a quadratic Lagrange basis function for each finite element of the physical domain considered. The impurity binding energies have been calculated numerically by solving the governing equations and compared with the variational method. The results we have obtained are in excellent agreement with those published in the literature.

Binding energy of hydrogenic donor impurity in [formula omitted] concentric double quantum rings: Effects of geometry, hydrostatic pressure, temperature, and aluminum concentration

We consider the effects of hydrostatic pressure, temperature, aluminum concentration and impurity position on hydrogen-like donor binding energy in GaAs/Ga1−xAlxAs concentric double quantum rings. The ground state energy and the impurity wave function are calculated using the variational method. For the hydrostatic pressure effects the Γ−X crossover has been taken into account. The probability density of electron without electron-impurity interaction have been investigated for different values of the sizes of the structure. The dependencies of the binding energy on geometry of the structure, hydrostatic pressure, temperature, aluminum concentration and impurity positions have been also investigated. The results show that the binding energy is an increasing (decreasing) function of the hydrostatic pressure and aluminum concentration (temperature). Additionally we have found that when the impurity is placed within the inner ring, the binding energy behavior strongly depends on the widths of the outer ring and coupling barrier.

Hydrogenic‐Donor Impurity Binding Energy Dependence of the Electric Field in GaAs/AlxGa1−xAs Quantum Rings

Using a variational method with two‐parameter trial wave function and the effective mass approximation, the binding energy of a donor impurity in GaAs/AlxGa1−xAs cylindrical quantum ring (QR) subjected to an external field is calculated. It is shown that the donor impurity binding energy is highly dependent on the QR structure parameters (radial thickness and height), impurity position, and external electric field. The binding energy increases inchmeal as the QR parameters (radial thickness and height) decrease until a maximum value for a central impurity and then begins to drop quickly. The applied electric field can significantly modify the spread of electronic wave function in the QR and shift electronic wave function from the donor position and then leads to binding energy changes. In addition, results for the binding energies of a hydrogenic donor impurity as functions of the impurity position and applied electric field are also presented.

Binding Energy Of A Donor In A Spherical Quantum Dot , GaAs

The binding energy of a donor in spherical quantum dots (QDs) is calculated, using a variational approach within the effective mass approximation. The binding energy is computed for GaAs QD as a function of the dot size for different impurity positions, and also as a function of the impurity position for different dot sizes. The results of mine show that when the impurity binding energy increases with the reduction in the dot dimension. The binding energy is also found to depend on the location of the impurity, and the same is the maximum for the on-center impurity. Also I found that the value of the polarizability obtained is several orders higher than the hydrogen atom value.

Stark effect-dependent of ground-state donor binding energy in InGaN/GaN parabolic QWW

Using the finite-difference method within the quasi-one-dimensional effective potential model and effective mass approximation, the ground-state binding energy of hydrogenic shallow-donor impurity in wurtzite (WZ) (In,Ga)N/GaN parabolic transversal-section quantum-well wires (PQWWs) subjected to external electric field is investigated. An effective radius of a cylindrical QWW describing the strength of the lateral confinement is introduced. The results show that (i) the position of the largest electron probability density in x–y plane is located at a point and it is pushed along the negative sense by the electric field directed along the positive sense, (ii) the ground-state binding energy is largest for the impurity located at this point and starts to decrease when the impurity is away from this point, (iii) the ground-state binding energy decreases with increase in the external electric field and effective radius, and (iv) the Stark-shift increases with the increase of the external electric field and the effective radius.

The effects of the hydrostatic pressure and temperature on binding energy and optical properties of a donor impurity in a spherical quantum dot under external electric field

The effects of the hydrostatic pressure and temperature on the electronic and the linear and nonlinear optical properties (i.e., absorption coefficients and refractive indices) are investigated in a spherical quantum dot in the presence of the electric field. The energy levels and wave functions are calculated using the variational method within the effective-mass approximation. The results show that these external factors have a significant effect not only on the binding energy of the donor impurity but also on the optical characteristics of the system. Moreover, it is found that the total absorption coefficient is strongly affected by the existence of impurity, the incident optical intensity, and relaxation time.

A study of the effect of spatial electric field on the binding energy and polarization of a donor impurity in a GaAs/AlAs tetragonal quantum dot (TQD)

In this work, the effects of spatial electric field and ratios of dot edge lengths (Lz/L) on the binding energy and polarization of a donor impurity in TQD are presented. Calculations are performed within the effective-mass approximation using the variational procedure and considering an infinite confining potential on all surfaces of the system. The binding energy and polarization are calculated as a function of (Lz/L) ratio. It is found that binding energy and polarization of a donor impurity in TQD depend strongly on the Lz/L ratio, applied spatial electric field strength and impurity position.

Pressure-dependent shallow donor binding energy in InGaN/GaN square QWWs

Using a variational approach, we perform a theoretical study of hydrostatic pressure effect on the ground-state of axial hydrogenic shallow-donor impurity binding energy in InGaN/GaN square quantum well wire (SQWWs) as a function of the side length within the effective-mass scheme and finite potential barrier. The pressure dependence of wire length, effective mass, dielectric constant and potential barrier are taken into account. Numerical results show that: (i) the binding energy is strongly affected by the wire length and the external applied pressure and (ii) its maximum moves to the narrow wire in particular for height pressure.

Binding Energy of D0 and D− Impurity Centers in CdTe/ZnTe Spherical Quantum Dot

Binding energy of neutral (D(0)) and negatively charged (D(-)) hydrogenic impurity located at the center of the CdTe/ZnTe spherical quantum dot has been investigated. Calculations are performed under the effective mass approximation on the basis of exact solution of the Schrödinger and Poisson equations. Eigenfunctions are expressed in terms of the Whittaker and Coulomb wave functions. Calculated results show that D(0) and D(-) impurity binding energies of ground 1s, 1S(1s2) and 2p, 3P(1s2p) excited states strongly depend on CdTe/ZnTe QD size if QD radius is less than one effective Bohr radius.

The effect of magnetic field on the impurity binding energy of shallow donor impurities in a Ga1−xIn x N y As1−y/GaAs quantum well

Using a variational approach, we have investigated the effects of the magnetic field, the impurity position, and the nitrogen and indium concentrations on impurity binding energy in a Ga1−xInxNyAs1−y/GaAs quantum well. Our calculations have revealed the dependence of impurity binding on the applied magnetic field, the impurity position, and the nitrogen and indium concentrations.

Ce3+ 5d-centroid shift and vacuum referred 4f-electron binding energies of all lanthanide impurities in 150 different compounds

A review on the wavelengths of all five 4f–5d transitions for Ce3+ in about 150 different inorganic compounds (fluorides, chlorides, bromides, iodides, oxides, sulfides, selenides, nitrides) is presented. It provides data on the centroid shift and the crystal field splitting of the 5d-configuration which are then used to estimate the Eu2+ inter 4f-electron Coulomb repulsion energy U(6,A) in compound A. The four semi-empirical models (the redshift model, the centroid shift model, the charge transfer model, and the chemical shift model) on lanthanide levels that were developed past 12 years are briefly reviewed. It will be demonstrated how those models together with the collected data of this work and elsewhere can be united to construct schemes that contain the binding energy of electrons in the 4f and 5d states for each divalent and each trivalent lanthanide ion relative to the vacuum energy. As example the vacuum referred binding energy schemes for LaF3 and La2O3 will be constructed.

Effects of hydrostatic pressure on the nonlinear optical properties of a donor impurity in a GaAs quantum ring

The effects of hydrostatic pressure, size quantization and impurity position on the binding energies of a hydrogenic-like donor impurity in a two-dimensional GaAs quantum ring and together with the linear and nonlinear intraband optical absorption and the relative refractive index changes are studied using the variational method and effective-mass approximation. The binding energies of 1s and 2s states are examined as functions of the structure (inner and outer radii), impurity position and hydrostatic pressure. We have also investigated the dependencies of the linear, nonlinear, and total optical absorption coefficients and relative index changes as a function of incident photon energy for different geometric configurations, hydrostatic pressure and impurity position. It is found that the variation of distinct sizes of the structure and impurity position leads to either a redshift and/or a blueshift of the resonant peaks of the intraband optical absorption and relative refractive index change spectrum. In addition we have found that the application of a hydrostatic pressure leads to a blueshift.

Sputtering of a silicon surface: Preferential sputtering of surface impurities

We present molecular-dynamics simulations of the sputtering of an impurity atom off a Si 2×1 (100) surface by 2 keV Ar ions. The impurity is characterized by its mass and its binding energy to the Si substrate. We find that sputtering strongly decreases with the mass and even more strongly with the binding energy of the impurity atom to the matrix. The velocity of the impurity perpendicular to the surface is reduced with increasing impurity mass and binding energy. In terms of available ionization theories we can conclude that heavier impurities will have a smaller ionization probability.

Tuning the binding energy of surface impurities in cylindrical GaAs/AlGaAs quantum dots by a tilted magnetic field

Using the potential morphing method in the framework of the effective-mass approximation, we have studied theoretically the effect of a tilted magnetic field on the binding energy of surface impurities in GaAs/Al0.3Ga0.7As cylindrical quantum dots. It is found that contrary to what was expected based on the existing literature for growth-direction magnetic fields, the presence of a tilted field does not always contribute positively to the binding energy of surface impurities. The shape (aspect ratio) and size of the cylindrical QD as well as the dopant positions at the QD surface play an important role. Furthermore, we find that decrease of the QD size can reduce the sensitivity of the variation of the donor binding energy with respect to the field strength (orientation), but it cannot change its general behaviour.

Improving the Solubility of Mn and Suppressing the Oxygen Vacancy Density in Zn0.98Mn0.02O Nanocrystals via Octylamine Treatment

Zn(0.98)Mn(0.02)O nanocrystals were synthesized by the wet chemical route and were treated with different content of octylamine. The environment around Mn and the defect type and concentration were characterized by photoluminescence, Raman, X-ray photoelectron spectroscopy, and X-ray absorption fine structure. It is found that N codoping effectively enhances the solubility of Mn substituting Zn via reducing donor binding energy of impurity by the orbital hybridization between the N-acceptor and Mn-donor. On the other hand, the O atoms released from MnO(6) and the N ions from octylamine occupy the site of oxygen vacancies and result in reduction of the concentration of oxygen vacancies in Zn(0.98)Mn(0.02)O nanocrystals.

BUILT-IN ELECTRIC FIELD EFFECT ON DONOR IMPURITIES IN STRAINED WURTZITE GaN/AlGaN ASYMMETRIC DOUBLE QUANTUM WELLS

The ground state binding energies of donor impurities in strained [0001]-oriented wurtzite GaN / Al x Ga 1-x N asymmetric double quantum wells are investigated using a variational method combined with numerical computation. The built-in electric field due to the spontaneous and strain-induced piezoelectric polarization and the strain modification on material parameters are taken into account. The variations of binding energies versus the width of central barrier, the ratio of two well widths, and the impurity position are presented, respectively. It is found that the built-in electric field causes a mutation of binding energies with increasing the width of central barrier to some value. The results for symmetrical double quantum wells and without the built-in electric field are also discussed for comparison.

Effects of external electric and magnetic fields, hydrostatic pressure and temperature on the binding energy of a hydrogenic impurity confined in a two-dimensional quantum dot

Based on the effective-mass approximation, simultaneous effects of external electric and magnetic fields, hydrostatic pressure and temperature on the binding energy of a hydrogenic donor impurity confined in a two-dimensional parabolic quantum dot have been studied, using the direct matrix diagonalization method. The binding energy dependencies upon the external electric field strength and direction, magnetic field, hydrostatic pressure and temperature are reported. The results reveal that the external electric and magnetic fields, hydrostatic pressure and temperature have a great influence on the impurity binding energy. Moreover, an increase in the tilt angle reduces the binding energy, especially at weak confinement regimes.