Abstract
We investigate the energy states of confined electrons in doped quantum structures with Razavy-like confining potentials. The theoretical investigation is performed within the effective mass and parabolic band approximations, including the influence of externally applied electric and magnetic fields. First, we analyze the case of a Razavy quantum well and determine its conduction subband spectrum, focusing on the lowest energy levels and their probability densities. These properties have been numerically determined by self-consistently solving the coupled system of Schrödinger, Poisson, and charge neutrality equations. Doping is introduced via an on-center $$\delta$$ -like layer. In order to evaluate the associated total (linear plus nonlinear) optical absorption coefficient (TOAC), we have calculated the corresponding diagonal and off-diagonal electric dipole matrix elements, the main energy separation, and the occupancy ratio which are the main factors governing the variation in this optical response. A detailed discussion is given about the influence of doping concentration as well as electric and magnetic fields, which can produce shifts in the light absorption signal, toward either lower or higher frequencies. As an extension of the self-consistent method to a two-dimensional problem, the energy states of quantum wire system of circular cross section, with internal doping and Razavy potential, have been calculated. The response of eigenvalues, self-consistent potentials and electron densities is studied with the variation in $$\delta$$ -doping layer width and of the donor density. Finally, the origin of Friedel-like oscillations, that arise in the density profile, generated by the occupation of internal and surface electronic states has been explained.
Highlights
Semiconductor structures based on quantum wells (QWs), quantum-well wires, and quantum dots have acquired a huge importance in the process of designing low-dimensional devices, mostly due to their features of charge carriers confinement
By using the effective mass and parabolic band approximations, the finite difference method, as well as a self-consistent calculation, we have investigated the features of total optical absorption coefficient of confined electrons in a delta-like doped Razavy-like quantum well under the combined effects of externally applied electric and magnetic field
A clear blue shift is evidenced for all the transitions studied, keeping the donor density fixed, the shift being more significant for changes in the electric field than in the magnetic field, in all cases a change in the magnitude of the optical absorption peaks is presented
Summary
Semiconductor structures based on quantum wells (QWs), quantum-well wires , and quantum dots have acquired a huge importance in the process of designing low-dimensional devices, mostly due to their features of charge carriers confinement. To satisfy the exigence required by new generation of optoelectronic devices, the involved semiconductor structures must be suitably selected upon the basis of their confinement potential geometry, their dimensions, and the possible influence of certain external physical factors Among these factors, we can cite the insertion of delta doped layers, as well as the application of either nonresonant intense laser field radiation, electric fields, magnetic fields, or a combination of these probe fields. Ungan et al reported on the optical responses in hyperbolic-like QWs under external electric and magnetic fields [23] They demonstrated that the TOAC and the total relative refractive index change coefficient can be shifted towards the blue or the red by adjusting the applied field intensities. They proved that the magneto-optical properties are largely affected by the external fields
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