A.A. Kirakosyan

Effect of the dielectric-constant mismatch and magnetic field on the binding energy of hydrogenic impurities in a spherical quantum dot

Abstract Within the effective mass approximation and variational method the effect of dielectric constant mismatch between the size-quantized semiconductor sphere, coating and surrounding environment on impurity binding energy in both the absence and presence of a magnetic field is considered. The dependences of the binding energy of a hydrogenic on-center impurity on the sphere and coating radii, alloy concentration, dielectric-constant mismatch, and magnetic field intensity are found for the GaAs–Ga 1− x Al x As–AlAs (or vacuum) system.

Electronic and intraband optical properties of single quantum rings under intense laser field radiation

The influence of an intense laser field on one-electron states and intraband optical absorption coefficients is investigated in two-dimensional GaAs/Ga0.7Al0.3As quantum rings. An analytical expression of the effective lateral confining potential induced by the laser field is obtained. The one-electron energy spectrum and wave functions are found using the effective mass approximation and exact diagonalization technique. We have shown that changes in the incident light polarization lead to blue- or redshifts in the intraband optical absorption spectrum. Moreover, we found that only blueshift is obtained with increasing outer radius of the quantum ring.

The effects of the intense laser and homogeneous electric fields on the electronic and intraband optical properties of a GaAs/Ga0.7 Al0.3As quantum ring

The simultaneous influences of an intense laser field and static electric field on one-electron states and intraband optical absorption coefficient are investigated in two-dimensional GaAs/GaAl0.3 As quantum ring. An analytical expression of the effective confining potential in the presence of the external fields is obtained. The one-electron energy levels and wave functions are calculated using the effective mass approximation and an exact diagonalization technique. We show that changes in the incident light polarization lead to blue- or redshifts in the intraband optical absorption spectrum. Moreover, we found that blueshift and redshift are induced by the simultaneous influences of an intense laser and lateral electric fields. The obtained theoretical results indicate a novel opportunity to tune the performance of quantum rings and to control their specific properties by means of intense laser and homogeneous electric fields.

Donor impurity-related linear and nonlinear intraband optical absorption coefficients in quantum ring: effects of applied electric field and hydrostatic pressure

AbstractThe linear and nonlinear intraband optical absorption coefficients in GaAs three-dimensional single quantum rings are investigated. Taking into account the combined effects of hydrostatic pressure and electric field, applied along the growth direction of the heterostructure, the energies of the ground and first excited states of a donor impurity have been found using the effective mass approximation and a variational method. The energies of these states are examined as functions of the dimensions of the structure, electric field, and hydrostatic pressure. We have also investigated the dependencies of the linear, nonlinear, and total optical absorption coefficients as a function of incident photon energy for several configurations of the system. It is found that the variation of distinct sizes of the structure leads to either a redshift and/or a blueshift of the resonant peaks of the intraband optical spectrum. In addition, we have found that the application of an electric field leads to a redshift, whereas the influence of hydrostatic pressure leads to a blueshift (in the case of on-ring-center donor impurity position) of the resonant peaks of the intraband optical spectrum.

The mobility of charge carriers in a size-quantized coated semiconductor wire

Within the f ofa staircase in2nitely deep potential well model, the mobility ofcharge carriers is calculated f scattering on impurity centers located on the axis ofa size-quantized semiconducting coated wire. Calculations are done for the dielectric constant mismatch of the wire, coating and surrounding environment, taking into account the di5erence ofthe e5ective masses in the wire and coating. The e5ect ofa longitudinal magnetic 2eld on mobility is also considered. Numerical results are presented for the GaAs–Ga1−xAlxAs system at di5erent values ofthe wire and coating radii, the alloy concentration x, and magnetic 2eld. ? 2002 Elsevier Science B.V. All rights reserved.

Effect of In and Al interdiffusion on electron states and light absorption in InxGa1−x As/AlyGa1−y As quantum dots

A new method of theoretical investigation of the interdiffusion effect on electron states in quantum dots is proposed. The main point of the method is the replacement of the “veritable” confining potential formed due to the diffusion by a model potential, for which the Schrödinger equation solutions and the energy spectrum are known. In the framework of the proposed method we calculate the positions of edges of the conduction and heavy hole bands and the absorption coefficient of interband transitions depending on the diffusion length in spherical InxGa1−xAs/AlyGa1−yAs quantum dots, using the Wood-Saxon potential as a model one.

Electron interaction with confined and interface polar optical phonons and electron mobility in quantum wires

Abstract The electron scattering in a cylindrical quantum wire embedded in a dielectric medium is studied by taking into account the phonon confinement effect. Expressions for intrasubband scattering rates have been obtained previously. Here using the Born approximation we obtain analytical expressions for intersubband scattering rates as well. Taking into account an inelasticity of the electron–phonon interaction the expressions for electron relaxation time and mobility are also derived. The predomination regions of different phonon modes and the phonon confinement effect on the scattering rate for intrasubband transitions are found. It is shown that the consideration of phonon confinement leads to mobility increase.

Linear dynamic polarizability and the absorption spectrum of an exciton in a quantum ring in a magnetic field

The problem of an electron–hole system interacting through a contact potential and moving in a one-dimensional quantum ring threaded by an Aharonov–Bohm flux is considered, with respect to the systems energetics as well as its optical properties. An exact analytical expression for the energy spectrum is derived using a straightforward method based on boundary conditions for wavefunctions and their derivatives along the ring. The optical properties of this exciton system, namely linear dynamic polarizability and the absorption spectrum, are investigated and certain unusual features are demonstrated. It is shown, for example, that for special values of the magnetic flux there are energies in the spectrum that correspond to the dark excitonic states.

Effect of a magnetic impurity on the optical properties of a spherical ZnSe quantum dot

We consider the electron and hole states in a semiconductor ZnSe spherical quantum dot, in the center of which a magnetic impurity atom of manganese is located. In calculations the quantum dot is approximated by a spherical rectangular well with a finite depth. Within the framework of perturbation theory, the effect of exchange spin interaction of an electron and a hole with a magnetic impurity on the band structure of the system is considered. The optical spectrum of the system for different polarizations of the incident light is studied also.

Intersubband absorption in quantum wire with a convex bottom in a magnetic field

The electron states in a cylindrical quantum well with a convex bottom in a magnetic field directed along the wire axis are investigated. The electron wavefunctions, depending on the quantum well characteristics and the magnetic field induction, are found. The absorption coefficient of a monochromatic linearly polarized light wave caused by intersubband transitions of electrons in the quantum wire is calculated. The selection rules are considered and analytical expressions for the absorption coefficient are presented for two cases of light wave polarization.