The effect of a strong magnetic field on the binding energy and the photoionization cross-section in a quantum well

Abstract

The effect of a strong magnetic field on the binding energy and the photon energy dependence of the photoionization cross-section as a function of the well size is studied in a quantum well for several values of the magnetic field, taking into account the finite character of the barrier potential. The results we have obtained show that the applied strong magnetic field affects drastically the binding energy and the photoionization cross-section and this effect is more significant in a quasi-two-dimensional structure than in a three-dimensional system.

The Photoionization Cross-Section of Impurities in Quantum Dots

“…It is important to mention that the increasing electronic confinement achieved by the reduction of the dimensionality by going from the three-dimensional system [66] to the quantum dot structures, going by way of the quantum well [54,57] and quantum-well wire [58,60] systems with small dimensions, causes the magnitude of the cross-section to become smaller and the peak of the cross-section to move towards the photoionization threshold energy. The peak at small photon energies is coming from the localization of the electronic wavefunction near the edge of the small systems.…”

“…The photon energy dependence of the photoionization cross-section in low-dimensional electronic systems is generally determined by the impurity ground state wavefunction, the potential which links the electron to the donor impurity and the conduction subband of the host crystal and by the wavefunction of the conduction subbands into which the charge carrier is excited. Recently, much attention has been devoted to the study of the hydrogenic impurity photoionization cross-section in systems with reduced dimensionality such as quantum wells [53][54][55][56][57][58] and quantum-well wires [59][60][61]. Most of these works can be summarized as follows: Takikawa et al [53] have experimentally and theoretically examined the photoionization of the deep traps in AlGaAs/GaAs multiple quantum well layers grown by metalorganic chemical vapour deposition.…”

“…More recently, the excitation energy dependence of the photoionization cross-section of a hydrogenic donor impurity in an infinite-barrier CdTe quantum well as a function of the well width, taking into account the interaction between electron and bulk longitudinal-optical phonons has been studied [57]. In a more recent work, Sali et al [58] have reported a calculation of the binding energies of a hydrogenic donor impurity associated with the first subband and the photoionization cross-section associated with a transition from the impurity ground state to the first conduction subband in a GaAs/Ga 1Àx Al x As quantum well in the presence of an applied strong magnetic field. The calculations have been performed by using the variational method, choosing a Gaussian trial wavefunction with two variational parameters for the impurity ground state that takes into accounts the confinement of the carriers in a finite well, the compression of the impurity atom in the (x, y)-plane by the application of an external strong magnetic field, and the electron-impurity Coulomb interaction.…”

The effects of temperature and hydrostatic pressure on the photoionization cross-section and binding energy of impurities in quantum-well wires

“…Lax [1] first investigated the photoionization cross-section of hydrogenic impurities in bulk semiconductors. In recent years, work has been done on the photoionization crosssection of hydrogenic impurities in dimensionally reduced structures such as quantum wells, wires and quantum dots [2][3][4][5][6][7][8][9][10]. It has been found that greater the confinement in such low-dimensional structures, greater the binding energy of these hydrogenic impurities.…”

“…Jayam and Navaneethakrishnan [6] have calculated the photoionization cross-section of donor impurities in quantum wells in an electric field. Recently Sali et al [7,8] have investigated the photoionization cross-section of impurities in quantum-well wires and quantum dots. Recently, Sali et al [9] have investigated the influence of a strong magnetic field on the ground state binding and photon energy dependence of the photoionization cross-section of a shallow donor impurity in a quasi-one-dimensional rectangular quantum wire with infinite and finite potential barriers using a variational approach.…”