Binding energy of hydrogenic impurity states in an inverse parabolic quantum well under static external fields (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.
Physica E: Low-dimensional Systems and Nanostructures, 2005
We have calculated variationally the ground state binding energy of a hydrogenic donor impurity in V-shaped quantum well (VQW) or full-graded GaAs=Ga 1Àx Al x As quantum wells in the presence of crossed electric and magnetic fields. These homogeneous crossed fields are such that the magnetic field is parallel to the heterostructure layers and the electric field is applied perpendicular to the magnetic field. The dependence of the donor impurity binding energy on the well width and the strength of the electric and magnetic fields are discussed. We hope that obtained results will provide important improvements in device applications, especially for narrow well widths and for a suitable choice of both fields.
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.
Journal of Applied Physics, 2011
The influence of thermal ionization of an impurity delta-doped layer situated either in the center or on the edge of a quantum well (QW) on impurity binding energy is investigated theoretically for the case of Si 0.8 Ge 0.2 /Si QW. It is shown that the Hartree potential created by free electrons and by ionized impurities at high temperatures superimposes on the original (at low temperature) QW energy profile. Resulting new QWs have their own impurity binding energies. It is of interest that energies are nearly the same for center-and edge-doped QWs, contrary to those at low temperatures. The obtained results are explained on the basis of Coulomb's law when decreasing the mean distance between free electron and impurity atom with temperature involves an increase in the impurity binding energy. V
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
Hydrogenic impurities in graded GaAs–(Ga,Al)As quantum-well wires in an electric field
Physica B: Condensed Matter, 2002
The electric field dependence of polarizability and binding energy of shallow-donor impurities in graded quantumwell wires is calculated by a variational method and in the effective-mass approximation. We have considered a finite confinement model and the results are compared with that of infinite confinement potential. Our calculations have revealed the dependence of the impurity binding and polarizability on the field direction in the graded quantum-well wire.