Binding Energy Of Hydrogenic Impurity Research Articles

Laser-dressed binding energy of a hydrogen impurity in the GaAs/AlxGa1 − xAs nanostructure in the presence of a static electric field

We set up a calculation for the ground-state binding energy of an on-center hydrogenic impurity in the simultaneous presence of intense high-frequency laser and static electric fields. It is shown that, although the individual external electric fields themselves act in a way to lower the binding energy of the impurity, one might accomplish a reduction of the weakening effects by considering the joint action of the two external fields. In addition, the variations of the binding energy of the impurity versus the laser field related parameter α0are adjusted by the external electric field. The position of the impurity binding energy maximum moves toward the higher values of α0on increasing the static electric field.

Binding energy of impurity states in spherical quantum dots with parabolic confinement

The binding energy of shallow hydrogenic impurities in spherical quantum dots (QDs) with parabolic confinement 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 show that 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.

Dielectric Confinement Effects on the Impurity and Exciton Binding Energies of Silicon Dots Covered with a Silicon Dioxide Layer

The binding energies of hydrogenic impurities and excitons in silicon (Si) dots modelled by a sphere covered with a silicon dioxide (SiO2) layer and embedded in various dielectric media, are calculated as a function of the sphere size and the thickness of the oxide. The strong-confinement limit was considered, so that all of the electrostatic interactions are treated as first-order perturbations considering the confined free-electron state as the unperturbed state. A recently proposed size correction for the dielectric constant of the Si dot is also taken into account. These calculations demonstrate the importance of the image-charge effect due to dielectric discontinuity. In addition, it is shown that the binding energies of the impurities and the excitons inside the silicon dots are greatly affected by alteration of the thickness of the oxides or the surrounding dielectric media.

Intense field effects on hydrogen impurities in quantum dots

Calculations of the binding energy of an on-center donor hydrogenic impurity in a quasizero-dimensional quantum-well system [quantum dot (QD)] placed in an intense, high-frequency laser field are presented. A nonperturbative theory and a variational approach are used as the framework for this calculation. The effect of the intense laser field is to “dress” the impurity potential making it dependent upon the laser field amplitude. A rapid decrease of the binding energy, for different values of the QD radius and for both infinite and finite potential barriers, with increasing field intensity is predicted. An application is made for a spherical QD made of GaAs/Ga1−xAlxAs heterostructures.

Hydrogenic impurities in a quantum well wire in intense, high-frequency laser fields.

Calculation of the binding energy of an axial donor hydrogenic impurity in an ideal, infinite, cylindrical quantum wire placed in an intense, high-frequency laser field is reported. By making use of a nonperturbative theory that ``dresses'' both the potential of the impurity and the confinement potential in the quantum wire, and the variational approach a rapid decrease of the binding energy for different values of the wire radius with increasing field intensity is predicted. \textcopyright{} 1996 The American Physical Society.

Screening in Semiconductor Nanocrystallites and Its Consequences for Porous Silicon.

Consequences of the modified dielectric properties of semiconductor crystallites are explored. The notion and usefulness of an effective dielectric constant are analyzed using a self-consistent linear screening calculation. The binding energy of hydrogenic impurities is defined and calculated, and it is shown why these are always ionized in porous silicon. Self-energy terms associated with the surface polarization charge are discussed in the context of Coulomb charging effects. Their contribution to exciton binding energies is also determined. Consequences of charging effects on carrier injection in porous silicon are finally considered and shown to be important.

Effect of spatially dependent screening on the binding energy of shallow impurities in spherical GaAs-(Ga,Al)As quantum dots

Within the effective-mass approximation and using a variational method the binding energies of hydrogenic impurities in spherical GaAs-(Ga,Al)As quantum dots are calculated considering the effect of a spatially dependent screening through an r-dependent dielectric response. It is found that the r-dependent dielectric response increases the binding energies when compared with those found using constant screening. The effect is more important for acceptors than for donors and must be taken into account in calculations that include the binding energies of acceptors impurities in GaAs-(Ga,Al)As quantum dots.

Hydrogenic Impurity States in Lateral-Surface-Modulation Quantum Wires11The project supported by National Committee of Education and NSF through Grant No. 69188006

We calculate hydrogenic impurity binding energy in quasi-one-dimensional GaAs/AlAs quantum wires with periodical lateral surface structure by making use of a variational approach. By a coordinate transformation, the structured interfaces of the wires are transformed into planar ones so that the boundary conditions of the electronic wave functions can be satisfied exactly on the interfaces. The dependence of the binding energies on the positions of the impurities and on the lateral surface structures is studied.

Effects of the image potential on hydrogenic impurity binding energies in quantum well wires

The effects of the image potential on hydrogenic impurity binding energies in quasi-one-dimensional GaAs/AlAs quantum well wires with a rectangular cross section are investigated. The results have shown that, when the impurity ion image potential is considered, the variations in binding energy are considerable and, when the impurity ion and electron image potentials are considered simultaneously, the corresponding variations in binding energy are small. The results also showed that the image potential is important, especially when the cross section dimensions of the quantum wire become small.

Effects of image potential on hydrogenic impurity states in quantum well wires

We calculate the effects of the image potential on hydrogenic impurity binding energies in quasi-one-dimensional GaAs/AlAs quantum well wires with a rectangular cross section. The results show that when the image potential of an impurity ion is considered the variations of the binding energies are remarkable, and that when the image potentials of an impurity ion and an electron are considered together the corresponding variations of the binding energies are small. The results also show that the image potential is important, especially when the cross section dimensions of the quantum wire become small.

Binding energies of hydrogenic impurities in lateral surface superlattice quantum well wires

A variational calculation of hydrogenic impurity binding energies in quasi-one-dimensional GaAs/AlAs quantum well wires with periodic lateral surface structures was carried out. By a coordinate transformation, the structured interfaces of the wires are transformed into planar interfaces so that the boundary conditions of the electronic wavefunctions can be satisfied exactly at the interfaces. The dependences of the binding energies on the positions of the impurities and on the lateral surface structure are studied.

Hydrogenic impurities in GaAs-(Ga,Al)As quantum dots.

The ground-state energy and the binding energy of shallow hydrogenic impurities in spherical GaAs-(Ga,Al)As quantum dots have been calculated as functions of the radius of the dot. The binding energy has been calculated following a variational procedure within the effective-mass approximation. We have used a finite confining potential well with depth determined by the discontinuity of the band gap in the quantum dot and the cladding. Calculations were also performed for an infinite confining potential. For the infinite potential well we found that the impurity binding energy increases as the dot radius decreases whereas in the finite potential-well situation, the binding energy reaches a peak value as the dot radius decreases and then diminishes to a limiting value corresponding to the radius for which there are no bound states in the well. We found that the strong electronic confinement in these quantum dots reflects itself in the ground-state energy and in the impurity binding energies, which are higher than those found in GaAs-(Ga,Al)As quantum wells and quantum-well wires.

Hydrogenic impurity states in the quantum well wires with lateral surface structures

We calculate hydrogenic impurity binding energies in quasi-one-dimensional GaAs AlAs quantum well wires with periodical lateral surface structures using a variational approach. By a coordinate transformation, the structured interfaces of the wires are transformed into planar ones so that the boundary conditions of the electronic wave functions can be satisfied exactly on the interfaces. The dependence of the binding energies on the positions of the impurities and on the lateral surface structures are studied.

The binding energy of hydrogenic impurities in quantum well structures under electric fields

The effect of an electric field on the hydrogenic impurity state in a quantum well is studied by using the variational-perturbative method. The variation of the binding energy as a function of the electric field with different well widths and impurity positions is calculated. We have also extended the calculation for the finite quantum well and some interesting points are discussed.

Binding energies and density of impurity states of shallow hydrogenic impurities in cylindrical quantum-well wires.

The binding energies of hydrogenic impurities in both infinite and finite GaAs-(Ga,Al)As cylindrical quantum-well wires are calculated as functions of the wire radius and of the impurity location in the well for different radii of the wires using a variational procedure within the effective-mass approximation. Assuming there is no intentional doping, we treat the impurity position as a random variable and define a density of impurity states that we have calculated as a function of the impurity binding energy. As a general feature, the density of impurity states presents two structures associated with impurities at the center and at the edge of the quantum-well wire that may be important in the understanding of absorption and photoluminescence experiments of doped GaAs-(Ga,Al)As quantum-well wires.

Barrier penetration effects for electrons in quantum wells: screening, mobility, and shallow impurity states

A two-dimensional electron gas in a quantum well confined by finite barriers is considered. We present analytical expressions for the finite confinement effects of a square-well potential and calculate the electron-electron interaction potential, the electron-impurity interaction potential, the interface-roughness scattering potential and the alloy-disorder scattering potential. The dielectric function of the interacting electron gas, the mobility (for charged-impurity scattering, for interface-roughness scattering, and for alloy-disorder scattering), and the binding energy of hydrogenic impurities (screened and unscreened) are discussed.

The binding energy of hydrogenic impurity in quantum well structures

We have studied the anisotropic effects on the hydrogenic impurity states in a quantum well. The variation of the binding energy of the ground state as a function of the well thickness for quantum wells with isotropic or anisotropic effective masses are calculated. The dependence of the longitudinal and transverse effective radii on the well size and the mass ratio m t/ m l is also discussed. A simple approximation method proposed recently by Lee and Mei are also used to study the binding energy of the hydrogenic impurity in the finite quantum well.

Effect of electron-phonon interaction on the hydrogenic impurity binding energy in a quantum well

Effect of electron-phonon interaction on the hydrogenic impurity binding energy in a quantum well

Binding energies of hydrogenic impurities in parabolic quantum wells.

We have calculated binding energies of simple, hydrogenic-type impurities in parabolic quantum wells as functions of the displacement of the impurity from the well center and the strength of the well potential. The calculation method is based on an expansion of the impurity wave function in a series of hydrogenic-type functions. Our results for the impurity at the well center are in excellent agreement with those obtained by a different method elsewhere.

Position-dependence of the impurity binding energy in quantum well wires

We present the results of variational calculations of the binding energy of hydrogenic impurities in quantum well wires with rectangular cross-section. The emphasis is placed on the dependence of the binding energy on the size of the wire cross section and on the positions of the impurity. The impurity binding energy decreases when the impurity position changes from the center of the wire to its edge or to one of the corners of the rectangular cross section.