Effect of external fields on the energies of hydrogenic donor with the anharmonic confinement potential (original) (raw)
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Physica B: Condensed Matter, 2003
We present a variational method to compute the binding energies for a hydrogenic impurity located at the center of the finite parabolic (PQW), V-shaped (VQW or full graded well) and square (SQW) GaAs-Ga 1Àx Al x As quantum wells under the electric field. The dependence of the ground state impurity binding energy on the applied electric field, the geometric shape of the quantum wells and well width is discussed together with the polarization effect.
Superlattices and Microstructures, 2000
The donor binding energies in finite GaAs/Ga x Al 1−x As quantum wells have been calculated by considering the confinement of electrons, which increases as the well width increases. The variational solutions have been improved by using a two-parameter trial wavefunction, and by including the conduction band nonparabolicity. It is shown that the method used gives results in agreement with those obtained in the experiments on the effective mass and the donor binding energy, both of which are strongly dependent on the well width.
The European Physical Journal B, 2009
Using the potential morphing method in the effective mass approximation, we have studied the behavior of the impurity binding energy as a function of the impurity position, for different applied electric fields, different Al concentrations at the well center, in strong, intermediate and weak confinement, for a GaAs/Ga 1Àx Al x As inverse parabolic quantum well. Our results indicate that the impurity binding energy has the same behavior as the spatial distribution of the electron ground state wavefunction and also that an electron localization appears only in the intermediate and weak confinement regime when the electric field takes non-zero values. r
Physical Review B
Binding energies of the ground state and of a few low-lying excited states of a hydrogenic donor in a quantum-well structure consisting of a single layer of GaAs sandwiched between two-semiinfinite layers of Ga~, Al"As are calculated, including the effect of nonparabolicity of the conduction band and following a variational approach. The effect of nonparabolicity of the conduction band is included by using an expression for the energy-dependent effective mass based on the k. p approximation. The variations of the binding energies of these states as a function of the size of the GaAs quantum well for different values of the potential barrier (or equivalently for different values of Al concentration x) are calculated. These results are compared with those obtained with the use of a parabolic conduction band.
Hydrogenic impurities in GaAs-(Ga,Al)As quantum dots
Physical Review B, 1992
The ground-state energy and the binding energy of shallow hydrogenic impurities in spherical GaAs-(Ga,A1)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 e8'ective-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 we11 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 rejects itself in the ground-state energy and in the impurity binding energies, which are higher than those found in GaAs-(Ga, A1)As quantum wells and quantum-well wires.
Physical Review B, 1992
The present work investigates the effect of image forces due to the dielectric mismatch in Ga& "Al"As/GaAs/Gal "Al"As superlattices on the binding energies of hydrogenic impurity atoms placed at the center of a Gal "Al"As/ GaAs/Gal "Al"As quantum well. The theory of images of classical electrodynamics is used to derive the potential energy of an impurity carrier (electron or hole) in a GaAs quantum well. Since the image-potential energy diverges as the charge approaches the interfaces, one can use the Lang-Kohn theory to study this system. It is pointed out that the image forces are important factors in studies of the binding energies of impurity atoms in GaAs quantum wells of narrow widths. Furthermore an accurate determination of image-plane locations in superlattice structures requires further investigations. I. INTRODUCTION Modern materials growth techniques, such as molecular-beam epitaxy (MBE) (Ref. l) and metal organic chemical vapor deposition (MOCVD), made it possible to fabricate systems consisting of alternate layers of two different semiconductors with controlled thickness and sharp interfaces. These new periodic structures are called superlattices. The most studied semiconductor superlattice consists of GaAs sandwiched between two Ga, "Al"As slabs (x is the aluminum mole fraction). Depending on the Al concentration, the band gap in Ga& "Al"As can be made considerably larger than that of GaAs. This leads to discontinuities of the conductionand valence-band edges at the interface I point. ' Until