Binding Energy Of Impurity Research Articles

Confinement effects on quasi 0D dimensional structure with AlxGa1-xAs/GaAs/AlxGa1-xAs quantum wells

In this work we study the effects of barrier height and position on symmetric AlxGa1-xAs/GaAs/AlxGa1-xAs quantum wells in absence of external influences. We use a variational method within the effective mass approximation to observe the effects on the structure. The donor trial function is taken as a product of the ground state wave function, with an arbitrary correlation function that depends only on ion-electron separation. It has been observed two peaks in the curves for the dependence of the ground-state binding energies versus the donor distance from the axis and it is shown that the impurity binding energy depends strongly on the impurity position, potential shape on both quantum wells.

Hydrostatic Pressure and Built-In Electric Field Effects on the Donor Impurity States in Cylindrical Wurtzite GaN/AlxGa1−xN Quantum Rings

Within the framework of the effective mass approximation, the ground-state binding energy of a hydrogenic impurity is investigated in cylindrical wurtzite GaN/AlxGa1-xNstrained quantum ring (QR) by means of a variational approach, considering the influence of the applied hydrostatic pressure along the QR growth direction and the strong built-in electric field (BEF) due to the piezoelectricity and spontaneous polarization. Numerical results show that the donor binding energy for a central impurity increases inchmeal firstly as the QR radial thickness(ΔR)decreases gradually and then begins to drop quickly. In addition, the donor binding energy is an increasing (a decreasing) function of the inner radius (height). It is also found that the donor binding energy increases almost linearly with the increment of the applied hydrostatic pressure. Moreover, we also found that impurity positions have an important influence on the donor binding energy. The physical reasons have been analyzed in detail.

Barrier Thickness and Hydrostatic Pressure Effects on Hydrogenic Impurity States in Wurtzite GaN/AlxGa1−xN Strained Quantum Dots

Within the framework of the effective mass approximation, barrier thickness and hydrostatic pressure effects on the ground‐state binding energy of hydrogenic impurity are investigated in wurtzite (WZ) GaN/AlxGa1−xN strained quantum dots (QDs) by means of a variational approach. The hydrostatic pressure dependence of physical parameters such as electron effective mass, energy band gaps, lattice constants, and dielectric constants is considered in the calculations. Numerical results show that the donor binding energy for any impurity position increases when the hydrostatic pressure increases. The donor binding energy for the impurity located at the central of the QD increases firstly and then begins to drop quickly with the decrease of QD radius (height) in strong built‐in electric fields. Moreover, the influence of barrier thickness along the QD growth direction and Al concentration on donor binding energy is also investigated. In addition, we also found that impurity positions have great influence on the donor binding energy.

Impurity Binding Energyin Quantum Dots with Parabolic Confinement in the Presence of Electric Field

We present an efficient method for calculation of the impurity binding energy in a quantum dot with parabolic confinement in the presence of the electric field. The unknown wave function is expanded into a basis of one-dimensional harmonic oscillator states describing the electron's movement perpendicular to the plane of quantum well. Green's function technique used to calculate the coefficients of the expansion. Binding energy of impurity states is defined as poles of the wave function. Developed method applied to calculation of impurity binding energy for different position of impurity and the intensity of electric field.

Combined Effects of Magnetic and Electric Fields on a Hydrogenic Impurity Binding Energy in a GaAs/GaAlAs Quantum Disc

Combined Effects of Magnetic and Electric Fields on a Hydrogenic Impurity Binding Energy in a GaAs/GaAlAs Quantum Disc

Impurity binding energies in quantum dots with parabolic confinement

We present an effective numerical procedure to calculate the binding energies and wave functions of the hydrogen-like impurity states in a quantum dot (QD) with parabolic confinement. The unknown wave function was expressed as an expansion over one-dimensional harmonic oscillator states, which describes the electron's movement along the defined z-axis. Green's function technique used to obtain the solution of Schredinger equation for electronic states in a transverse plane. Binding energy of impurity states is defined as poles of the wave function. The dependences of the binding energy on the position of an impurity, the size of the QD and the magnetic field strength are presented and discussed.

Binding Energy of Donor Impurity in a Rectangular Semiconductor GaAs Quantum Dot with Electric Field

Within the quasi-one-dimensional effective potential model and effective mass approximation, we calculate the ground and the first few excited state binding energies of a donor impurity in a rectangular quantum dot (RQD) in the presence of electric field. We discuss detailedly dependence of the binding energies on the impurity positions. The results show that the binding energy is the largest when the impurity is located at the center of RQD with zero field and is lowest when the impurity is located at the corner of the RQD. The peak strengths and positions of the probability density in RQD appear to be the critical control on such impurity-induced dependence. We believe our results can provide an indication for design of some photoelectric devices constructed based on GaAs RQD structures.

The effect of hydrostatic pressure on the binding energy and diamagnetic susceptibility of a laser dressed donor impurity in a GaAs/GaAlAs nanowire superlattice

In this paper the effects of hydrostatic pressure and laser radiation on the binding energy and diamagnetic susceptibility of an off-center hydrogenic donor impurity in a nanowire superlattice (NWSL) are studied. The energy eigenvalues and corresponding wave functions of ground and first excited states are numerically computed using finite difference method for a NWSL with circular cross-section which involved an array of spherical quantum dots (QDs). The numerical results show that oscillatory behaviors appear in binding energies and diamagnetic susceptibilities of ground and first excited states as impurity shifts away from center of QDs. Maximum values of ground state binding energy (first excited state binding energy) occur when impurity is located at the center of QDs (at the center of barriers). Additionally, binding energies of ground and first excited states shift towards higher (lower) energies as pressure (laser radiation) increases. An opposite behavior is observed for absolute value of diamagnetic susceptibility as pressure or laser radiation increases. Also, as the QDs’ volume increases the binding energies (I) decrease or (II) increase, reach maximum values and then decrease; which strongly depend on the position of impurity.

On some new effects in delta-doped QWs

Self-consistent calculation of Schrodinger, Poisson and electroneutrality equation with embedded impurity binding energy calculations of delta-doped SiGe/Si quantum well structures are performed. The influence of several parameters of the structure on the impurity binding energy is studied and discussed. On the basis of found phenomena the idea of an optical modulator controlled by a weak electric field is put forward.

Binding energy of the ground and first few excited states of hydrogenic donor impurity in a rectangular GaAs quantum dot in the presence of electric field

Within the quasi-one-dimensional effective potential model and effective mass approximation, we calculate the ground and the first 9 excited-state binding energies of a hydrogenic donor impurity in a rectangular quantum dot (RQD) in the presence of electric field. The analytical form of the quasi-one-dimensional effective potential replacing the three-dimensional Coulomb potential in our model is derived by Fourier transforms. We discuss detailedly dependence of the binding energies on the impurity positions and electric fields. For the ground-state binding energy, our results qualitatively agree with that of Mendoza et al. (2005) in which they only calculated the ground-state binding energies in cubic quantum dots by variational method. However, for first 9 excited-state binding energies, such dependence has complex manner since there are two or three peaks in the electronic probability density distribution curves. The strengths and positions of these peaks in RQD affect the interaction potential between electron and impurity, which appears to be the critical control on the binding energies of impurity. The applied electric field pushes the positions of these peaks downwards, and the strengths of peaks located at the upper half of RQD increase while the strengths of lower peaks firstly decrease, then increase with increasing electric field. The high peak strength can lead to increase of the binding energy while the large distance between the position of peak and impurity center results in reduce of the energy, which is an interesting competition. This competition is more obvious for excited-state binding energies of off-central impurity.

Dielectric mismatch and shallow donor impurities in GaN/HfO2 quantum wells

In this work we investigate electron–impurity binding energy in GaN/HfO2 quantum wells. The calculation considers simultaneously all energy contributions caused by the dielectric mismatch: (i) image self-energy (i.e., interaction between electron and its image charge), (ii) the direct Coulomb interaction between the electron–impurity and (iii) the interactions among electron and impurity image charges. The theoretical model account for the solution of the time-dependent Schrödinger equation and the results shows how the magnitude of the electron–impurity binding energy depends on the position of impurity in the well-barrier system. The role of the large dielectric constant in the barrier region is exposed with the comparison of the results for GaN/HfO2 with those of a more typical GaN/AlN system, for two different confinement regimes: narrow and wide quantum wells.

Impurity binding energy for δ-doped quantum well structures

The binding energy of an impurity delta layer situated either in the centre or at the edge of a quantum well (QW) is theoretically considered for the example of n-type Si0.8Ge0.2/Si/Si0.8Ge0.2 QW doped with phosphorus. Calculations are made for the case of not so big impurity concentrations, when impurity bands are not yet formed and it is still possible to treat impurity as isolated ones. It is shown on the base of self-consistent solution of Schrödinger, Poisson and electro-neutrality equations that impurity binding energy is dependent on the degree of impurity ionization and the most noticeably for the case of edge-doped QWs.

Effects of a high intensity laser in the binding energy of a donor impurity

En este trabajo presentamos los resultados teoricos de los efectos de un laser intenso en la energia de enlace en el estado base de una impureza donadora neutra Ubicada en un pozo cuantico de gaas(Ga,Al)As embebido a su vez en un hilo cuantico. Calculamos el comportamiento de la energia de enlace teniendo en cuenta diferentes parametros como el radio del hilo, la intensidad del haz laser, las diferentes concentraciones de aluminio en la heteroestructura y de la posicion de la impureza dentro del pozo cuantico; al variar este ultimo parametro pudimos observar un nuevo comportamiento de esta energia en presencia de un laser intenso.

Effect of external fields on the energies of hydrogenic donor with the anharmonic confinement potential

The impurity binding energy in the GaAs−Ga1−xAlxAs system is studied with an anharmonic type confinement potential by taking into account the influence of the external electric and magnetic fields within the framework of the effective mass approximation and asymptotic iteration method (AIM). The influence of the external electromagnetic fields and anharmonicity on a donor binding energy is examined systematically. It is shown that the donor binding energy is highly dependent on the external electric and magnetic fields and the confinement potential shapes. Both the electric and magnetic fields are increased, the binding energies increase for each of them. However, the behaviors of increase in the weak and strong fields’ regimes have different character a bit. Furthermore, when the more anharmonicity is considered, the binding energy of donor slightly increases as well.

Effect of electric and magnetic fields on impurity binding energy in zinc-blend symmetric InGaN/GaN multiple quantum dots.

The binding energy of ground state for hydrogenic impurity in multiple quantum dots is calculated in the framework of effective-mass approximation and using a variational method. It is shown that the binding energy is a function of the size of dots, impurity position and external fields strength. The binding energy has a maximum value when the impurity is located on the center of dots and decreases for other impurity positions. The external electric and magnetic fields change the magnitude and the position of peaks. PACS Codes 73.20.D; 71.21.La; 71.55.Eq

Hydrogenic impurity states in a parabolic quantum dot: Hydrostatic pressure and electric field effects

The binding energy of hydrogenic impurity associated with the ground state and some low-lying states in a GaAs spherical parabolic quantum dot with taking into account hydrostatic pressure and electric field are theoretically studied by using the configuration–integration method. The binding energies of these low-lying states of the impurity depend sensitively on the hydrostatic pressure, electric field and the strength of the parabolic confinement. Based on the analysis of these impurity states, we propose a way for preparation of quantum bit (qubit) by using the strong quantum confinement to the impurity in the quantum dot. Also we calculate the wave functions of some low-lying states to discuss the oscillator strength which is related to the electronic dipole-allowed transitions from 0s state to 0p state. The results show that the electronic dipole-allowed transitions mostly happen between the 0s state and 0p state, especially for the quantum confinement large enough.

Impurity-related photoionization cross section in a pyramid-shaped quantum dot: Intense laser field and hydrostatic pressure effects

Within the effective mass approximation the binding energy and photoionization cross section of a donor impurity in a pyramid shaped quantum dot under simultaneous action of the hydrostatic pressure and high-frequency laser field have been investigated. We found that: (i) the variation of the binding energy reflects the spatial distribution of the impurity wave function, which is significantly modified by the laser radiation; (ii) the photoionization cross section and resonant peak magnitude depend on the donor position, laser field intensity and pressure. The localization of resonant peak maxima in the doping planes and their dependence on external perturbations are systematically investigated.

Impurity-related nonlinear optical properties in delta-doped quantum rings: Electric field effects

Using a variational procedure within the effective mass approximation, we have calculated the donor impurity binding energy for the ground (1s-like) and the excited (2pz-like) states as well as the impurity-related nonlinear optical absorption and relative changes in the refraction index in a GaAs single quantum ring with axial n-type delta-doping. The delta-like potential along the z-direction is an approximate model analytically described using a Lorentzian function with two parameters. Additionally we consider the application of an electric field along the z-direction. It is found that the changes in the geometry of the quantum ring, the change in the 2D impurity density of the delta-like doping, and different values of the electric field lead to a shifting of the resonant peaks of the optical responses spectrum.

Binding energies of impurity states in strained wurtzite GaN/AlxGa1−xN heterojunctions with finitely thick potential barriers

Ground state binding energies of donor impurities in a strained wurtzite GaN/AlxGa1−xN heterojunction with a potential barrier of finite thickness are investigated using a variational approach combined with a numerical computation. The built-in electric field due to the spontaneous and piezoelectric polarization, the strain modification due to the lattice mismatch near the interfaces, and the effects of ternary mixed crystals are all taken into account. It is found that the binding energies by using numerical wave functions are obviously greater than those by using variational wave functions when impurities are located in the channel near the interface of a heterojunction. Nevertheless, the binding energies using the former functions are obviously less than using the later functions when impurities are located in the channel far from an interface. The difference between our numerical method and the previous variational method is huge, showing that the former should be adopted in further work for the relevant problems. The binding energies each as a function of hydrostatic pressure are also calculated. But the change is unobvious in comparison with that obtained by the variational method.

1s-like state binding energy of a donor impurity bound to Xz valleys of GaAs/AlAs type II quantum dots with an uniform applied magnetic field

In this paper we calculate the binding energy of a donor impurity in the 1s-like state bound to X valleys of GaAs/AlAs type II quantum dots, using an anisotropic variational method, which allows us to take into account the anisotropy of the effective mass and quantum confinement. The binding energy is plotted against the radius of the cylinder and the uniform magnetic field applied along the cylinder axis. The binding energies have a monotone behavior with the cylinder radius for different magnetic fields and almost constant behavior with increasing magnetic field.