Binding Energy Of Impurity Research Articles

Fundamental optical transitions in hexagonal boron nitride epilayers

Fundamental optical transitions in hexagonal boron nitride (h-BN) epilayers grown on sapphire by metal–organic chemical vapor deposition (MOCVD) using triethylboron as the boron precursor have been probed by photoluminescence (PL) emission spectroscopy. The low temperature (10 K) PL spectrum exhibits two groups of emission lines. The first group includes the direct observation of the free exciton and impurity bound exciton (BX) transitions and phonon replicas of the BX transition, whereas the second group is attributed to the direct observation of the band-to-band transition and its associated phonon replicas. The observations of zero-phonon lines of the band-to-band and exciton transitions, which are supposedly forbidden or “dark” in perfect h-BN crystals, result from a relaxed requirement of momentum conservation due to symmetry-breaking in the presence of high concentrations of impurities/defects and strain, which in turn provided more deterministic values of the energy bandgap (Eg), exciton binding energy (Ex), and binding energy of impurity bound excitons (EBX) in h-BN epilayers. Excitonic parameters of h-BN epilayers grown by MOCVD, carbon-free chemical vapor deposition, and high purity h-BN bulk materials are compared and discussed. The present results, together with available information in the literature, represent a significant improvement in the understanding of the fundamental optical properties and excitonic parameters of h-BN ultrawide bandgap semiconductors.

Impact of combined electric and magnetic fields on the physical properties of GaAs variant quantum ring quarter cross-section in presence of an off-center shallow donor impurity

In this study, we explored the complex effects of electric fields in three unique directions and axial magnetic field on a GaAs-Variant Quantum Ring Quarter Cross-Section (VQRQCS), particularly when there is an off-center shallow donor impurity. The investigation explores the impact of these fields on various physical attributes, including electronic energy, binding energy, magnetic shift, Stark shift, average electron impurity distance, and diamagnetic susceptibility. Using effective mass approximation and three-dimensional finite difference methods we solved the Schrodinger equation. Our result shows that the geometric radius of the VQRQCS has an essential impact on electronic energy. Notably, as the radius increases, the electronic energy decreases, regardless of the presence of fields. In particular, we found that magnetic fields amplify the electronic energy of the ground state. The angle of curvature of the nanostructure and the direction of the electric field also play an important role. Additionally, the electron–impurity binding energy decreases with the growth of the nanostructure, with external fields intensifying this effect. The average distance between the electron and the impurity, analyzed in the context of simultaneously applied fields, provides insight into the Coulomb interaction. Diamagnetic susceptibility, measuring the response of a material to an external magnetic field, is studied, indicating opposition to the external field. In summary, this research highlights the nuanced interactions between electric and magnetic fields that determine the properties of a GaAs quantum ring, providing critical insights for quantum ring-based technological advancements.

Quantum size effect on discrete states of a hydrogenic impurity in a core/shell nanowire

The hydrogenic impurity states in a core/shell nanowire is studied by a variational method combined with a finite-difference algorithm. The quantum size effect on the wavefunction localization and energy levels at the ground state and lowing-excited eigenstates are analyzed by changing the core radius or shell composition. The transition from discrete states (confined) to extended states (continuum) will occur if changing the core radius or shell composition to a certain critical value. The ground-state binding energy of the hydrogenic impurity in the core/shell nanowire shows different variation trends with radius and composition.

Spin-orbit interaction effects on electronic, magnetic, and optical properties of [formula omitted]- center in a quantum dot with Gaussian confinement

In this paper, we study the binding energy, transition energy, and oscillator strength of a D0 impurity positioned at the center of a two-dimensional quantum dot. The QD is subject to a Gaussian confining potential, magnetic field, Rashba, and Dresselhaus spin-orbit interactions (SOI). The ground state and first exited state energies, and corresponding binding energies are calculated. Using the variational method with simple wave functions, transition energy, magnetic moment, and susceptibilities are obtained as a function of QD parameters, magnetic field, and SOI coupling strengths. The energies and binding energies increase with Dresselhaus SOI strength but decrease with Rashba SOI strength in a magnetic field. The magnetic moment and susceptibility of both states of a (D0) impurity show diamagnetic behaviour with both SOI strengths. Finally, we studied oscillator strength and compared the available literature, which did not consider all these effects.

Electronic and optical properties of CdSe/ZnSe core/shell QDs within centered hydrogenic impurity and their tunability when subjected to an external electric field

The electronic and optical properties of CdSe/ZnSe semiconductor core/shell quantum dots with hydrogenic donor impurity were investigated theoretically. The perturbation approach and variational method were used in calculations under Effective Mass Approximation. The considered structure is embedded in a variable polymer matrix. The binding energy (BE), photoionization cross-section, polarizability, and diamagnetic susceptibility of the excited impurity were calculated first according to the core/shell radius ratio and then under a significant external electric field and in the absence of an external electric field. A significant stark shift was observed in the BE relative to the embedded matrix element.

Unveiling the Role of Donor Impurity Position on the Electronic Properties in Strained Type I and Type II Core/Shell Quantum Dots under Magnetic Field.

In this theoretical investigation, we delve into the significant effects of donor impurity position within core/shell quantum dot structures: type I (CdTe/ZnS) and type II (CdTe/CdS). The donor impurity's precise location within both the core and the shell regions is explored to unveil its profound influence on the electronic properties of these nanostructures. Our study investigates the diamagnetic susceptibility and binding energy of the donor impurity while considering the presence of an external magnetic field. Moreover, the lattice mismatch-induced strain between the core and shell materials is carefully examined as it profoundly influences the electronic structure of the quantum dot system. Through detailed calculations, we analyze the strain effects on the conduction and valence bands, as well as the electron and hole energy spectrum within the core/shell quantum dots. The results highlight the significance of donor impurity position as a key factor in shaping the behaviors of impurity binding energy and diamagnetic susceptibility. Furthermore, our findings shed light on the potential for tuning the electronic properties of core/shell quantum dots through precise impurity positioning and strain engineering.

Optical absorption in core–shell quantum antidot with donor impurity under applied co-directed electric and magnetic fields

In this article, we have investigated an electron energy spectrum, optical absorption coefficients (OACs) and polarizability under the effect of the co-directed electric and magnetic fields in the multilayer spherical quantum antidot (MSQAD) Al0.3 Ga0.7 As/GaAs/Al0.3Ga0.7 As with off-center impurity. The calculations were done for different dot sizes within the effective mass approximation using the matrix method. The dependence of the total, linear, and nonlinear OACs on the incident photon energy is calculated considering the intraband electron quantum transitions. The donor polarizability and impurity binding energy as function of electric field intensity are obtained at different values of the magnetic field induction.

Tuning of binding energy, polarizability and photoionization cross-section of a hydrogenic impurity in CdTe/ZnTe core-shell nanostructure by the electric field and capped matrix

The current work describes in detail the effect of polarization charges on the electronic properties of core/shell spherical quantum dots (CSQDs) structures composed of CdTe/ZnTe semiconductors. In the calculations, energy levels and wave functions matching these levels were calculated by using the effective mass approach (EMA). Furthermore, the binding energy of a hydrogenic impurity was calculated under the variational approach. The matrix effects surrounding the CSQDs structure, the quantum dot size, the impurity, and how the applied external electric field affects the impurity binding energy (Eb), polarizability (Pa) and photoionization cross-section (PICS) are calculated and discussed in detail. The obtained results revealed that the Eb, the PICS and Pa are not only affected by the quantum parameter size but also by the capped matrix, the impurity and external electric field EF actions.

Hydrogen-like Impurity States in β-Ga2O3/(AlxGa1−x)2O3 Core/Shell Nanostructures: Comparison between Nanorods and Nanotubes

The binding energy of an off-center hydrogen-like impurity in an ultra-wide band gap β-Ga2O3/(AlxGa1−x)2O3 core/shell nanostructure is studied using a variational method combined with a finite-difference algorithm. Four impurity states with the radial and axial quantum numbers being 0 or 1 in two kinds of core/shell nanostructures, including nanorods and double-walled nanotubes, are taken into account in the numerical calculations. The variation trends in binding energy corresponding to the four impurity states as functions of structural dimension and Al composition differ in nanorods and nanotubes when the impurity moves toward the interface between the Ga2O3 and (AlxGa1−x)2O3 layers. The quantum confinement due to the structural geometry has a considerable influence on the probability density of the impurity states as well as the impurity binding energy. The numerical results will pave the way toward theoretical simulation of the electron states in rapidly developing β-Ga2O3 low-dimensional material systems for optoelectronic device applications.

Trapped Ideal Bose Gas with a Few Heavy Impurities

In this article, we formulate a general scheme for the calculation of the thermodynamic properties of an ideal Bose gas with one or two immersed static impurities, when the bosonic particles are trapped in a harmonic potential with either a quasi-1D or quasi-2D configuration. The binding energy of a single impurity and the medium-induced Casimir-like forces between the two impurities are numerically calculated for a wide range of temperatures and boson–impurity interaction strengths.

Binding energy and photoionization cross section of piezoelectric core/shell quantum dots

We have studied the binding energy and photoionization cross section of a donor impurity in core/shell piezoelectric quantum dots within the framework of the effective-mass approximation. A size-dependent internal piezoelectric field along the axis of the quantum dot caused by the lattice-mismatch induced strain has been described by a full analytical model. The results show that the photoionization cross section and binding energy become largest when the impurity is at the center of QD. The photoionization cross section in wurtzite structure is much larger than that in zinc blende structure, the optimal ratio of Rc/Rs to maximize the peak value of photoionization cross is between about 0.6 and 0.7.

Influence of impurity binding energy on the excitation dynamics of doped GaAs quantum dot: Role of noise

Influence of impurity binding energy on the excitation dynamics of doped GaAs quantum dot: Role of noise

The impact of the electric field on the photoionization cross section, polarizability, and donor impurity binding energy in multilayered spherical quantum dot

The impact of the electric field on the photoionization cross section, polarizability, and donor impurity binding energy in multilayered spherical quantum dot

Impurity Properties of Inversion Layers with Electronic and Substrate Quantum Screening

In this paper, the combined effect of electronic and substrate screening on impurity states in inversion layers is investigated theoretically. An explicit expression of the screened impurity interaction potential with an effective screening parameter, depending on the material and structural parameters, is established analytically for the first time. The main physical results are (a) an enhancement of the carrier saturation effect and (b) the dependence of the nature of the screening mechanism on the dielectric type (low-κ and high-κ) of the oxide layer. An experimentally measurable impurity binding energy is studied and numerically presented for realistic InSb/SiO2/SiO2/metal (ll-) and InSb/S(sulfur)/HfO2/metal (lh-κ type) multi-layer structures. A substantial enhancement of the binding energy is obtained with the non-degenerate Q2D EG for the ll-κ-type structure, reaching an almost fourfold value of the InSb bulk sample (~0.66 meV).

Effects of applied magnetic field and pressure on the diamagnetic susceptibility and binding energy of donor impurity in GaAs quantum dot considering the non-parabolicity model’s influence

ABSTRACT In this article, we investigate the influence of the hydrostatic pressure, magnetic field, and conduction band non-parabolicity on both the diamagnetic susceptibility and the binding energy of shallow donor impurity in a quantum disk made out of GaAs. The Hamiltonian of the investigated problem has been solved within the framework of the effective-mass approximation. The energy minimisation has been performed using a variational approach. Our results reveal that both the diamagnetic susceptibility and binding energy have been reduced with increasing the disk size. Moreover, the diamagnetic susceptibility increases as the impurity moves from the extremity to the centre of the disk. However, both the diamagnetic susceptibility and binding energy have been improved under applied magnetic field, hydrostatic pressure, and by considering the conduction band non-parabolicity model as well. We hope that the reported results will be a modest contribution to further theoretical research in the field of nanostructures.

Hydrogenic donor impurity states and intersubband optical absorption spectra of monolayer transition metal dichalcogenides in dielectric environments

The hydrogenic donor impurity states and intersubband optical absorption spectra in monolayer transition metal dichalcogenides (ML TMDs) under dielectric environments are theoretically investigated based on a two-dimensional (2D) nonorthogonal associated Laguerre basis set. The 2D quantum confinement effect together with the strongly reduced dielectric screening results in the strong attractive Coulomb potential between electron and donor ion, with exceptionally large impurity binding energy and huge intersubband oscillator strength. These lead to the strong interaction of the electron with light in a 2D regime. The intersubband optical absorption spectra exhibit strong absorption lines of the non-hydrogenic Rydberg series in the mid-infrared range of light. The strength of the Coulomb potential can be controlled by changing the dielectric environment. The electron affinity difference leads to charge transfer between ML TMD and the dielectric environment, generating the polarization-electric field in ML TMD accompanied by weakening the Coulomb interaction strength. The larger the dielectric constant of the dielectric environment, the more the charge transfer is, accompanied by the larger polarization-electric field and the stronger dielectric screening. The dielectric environment is shown to provide an efficient tool to tune the wavelength and output of the mid-infrared intersubband devices based on ML TMDs.

Photoionization cross section of donor single dopant in multilayer quantum dots under pressure and temperature effects

The shallow donor single dopant confined in the multilayer cylindrical quantum dots is investigated numerically within the framework of effective-mass approximation. The Schrödinger equation that governs the wave function of a complicated system is solved numerically by the finite element method using the Python programming language. The results indicate that the photoionization cross section (PCS) is similar to the Gauss function curve, the height of the curve's peak is proportional to oscillator strength, and the center peak position is related to the impurity binding energy. These two last parameters are dependent on the distribution of probability density across each part of the system. The probability density is tuned by the electron confinement and optical transition. The augmentation of dot radius or temperature decreases the electron confinement, which causes a redshift of PCS, and the presence of hydrostatic pressure blue shifts the PCS. On the other side, As the dot radius and hydrostatic pressure are increased, the oscillator's strength increases, raising values near the critical energy, and vice versa for temperature.

Study of photoionization cross section and binding energy of shallow donor impurity in multilayered spherical quantum dot

In the framework of the effective mass approximation and by using the finite element method , we have studied the simultaneous effects of position dependent effective mass (PDEM) and dielectric function on the shallow donor impurity binding energy and photoionization cross section in a multilayered spherical quantum dot . We have also investigated the influence of conduction band nonparabolicity and polaronic mass on the both binding energy and photoionization cross section (PCS). The obtained results have shown that the nonparabolicity and polaronic mass effects enhance the binding energy and photoionization cross section. Furthermore, it can be concluded from this research that the binding energy and the PCS are strongly dependent on the geometrical parameters, and PDEM. Changes in binding energy and photoionization cross section have physical reasons, which are discussed in details. • The photoionization cross section (PCS) and the binding energy are strongly dependent on the width of the structure layers. • The conduction band nonparabolicity and the polaronic mass effects enhance the binding energy and reduce the PCS peak magnitude. • The dependence of the dielectric function ε ( r ) on the electron coordinates makes the amplitude peak of the PCS take high values.

The intensity and direction of the electric field effects on off-center shallow-donor impurity binding energy in wedge-shaped cylindrical quantum dots

• In the effective mass approximation, the finite difference method is adopted. • Electric field effect on donor binding energy in a wedge quantum dot is obtained. • The geometrical parameters effects (radius, height and opening) have been affected. • The six confined electronic states dependent on dot shape have been examined. Taking into account an infinite confinement potential, including the influence of external electric field applied in different directions, we have systematically examined the different factors that lead to changes in the ground state binding energy between the hydrogen impurity and the electron, which are confined in a wedge-shaped cylindrical quantum dot (WSCQD) of radius R , height H and azimuthal angle θ m . The resolution of the Schrödinger equation in three dimensions is achieved by the numerical finite difference method. The binding energy is calculated for several quantum dot geometry, various electric field direction, and different position of the impurity located on the first rectangular surface or inside the WSCQD. We have obtained that the direction of the electric field has an important influence on the binding energy of the off-center impurity. We have discussed in detail the weak effect of the radial electric field in the critical value of the WSCQD azimuthal angle θ m = 76.20 ∘ for R = 30 nm and H = 50 nm. The competition between the different effects, such as the electric field direction, the impurity position, and the no-symmetry of the WSCQD, on the electron-impurity distance, is physically interpreted in this paper. To make a more self-contained work, the finite confinement potential effects have also been discussed. Calculations have also been validated by using the finite element method.

Intense terahertz laser field induced electro-magneto-donor impurity associated photoionization cross-section in Gaussian quantum wires

Using expressions derived within the compact density matrix approach, the peaks of optical absorption and the changes of refractive index of a hydrogenic impurity in a GaAs/GaAlAs Gaussian quantum well wire are calculated taking into account the influence of static electric, magnetic and intense laser fields. The photoionization cross section, with normalized photon energy, is computed for different values of static electric field, magnetic field, and laser dressing parameter. The dipole moment matrix elements and the transition energy between ground and first excited state energy levels are computed as functions of quantum wire width and confinement potential depth, with and without external perturbations. Donor impurity binding energy is investigated in presence of the aforementioned electromagnetic probes, using parabolic band and effective mass approximations. The results show that the absorption coefficients depend on the transition energy difference between initial and final states involved as well as on the corresponding polarization response via dipole matrix elements. Discussed optical properties are field-sensitive and they can be tuned within the desired energy ranges using these external perturbations. • Peaks of optical absorption and changes of refractive index of a hydrogenic impurity in a GaAs/GaAlAs Gaussian quantum well wire are calculated. • They have been computed taking into account the influence of static electric, magnetic and intense laser fields. • Photoionization cross section, with normalized photon energy, is computed. • Donor impurity binding energy is investigated in the presence of aforementioned electromagnetic-probes, using parabolic band and effective mass approximations. • Discussed optical properties are field-sensitive and they can be tuned within the desired energy ranges using these external perturbations.