Binding Energy And Absorption of Donor Impurity In Spherical GaAs/AlxGa1-x As Quantum Dots With Konwent Potential

In this study, the electronic and optical properties of single or core/shell quantum dots, which are formed depending on the parameters in the selected Konwent potential, are investigated. Namely, the effects of the size and geometric shapes of quantum dots on the binding energy of the on-center donor impurity, the total absorption coefficient and refractive index which are including transitions between the some confined states, and the electromagnetically induced transparency between the lowest six confined states related to the donor impurity are investigated. We have used the diagonalization method by choosing a wave function based on the Bessel and Spherical Harmonics orthonormal function to find the eigenvalues and eigenfunctions of the electron confined within the quantum dots which have different types mentioned above. To calculate the optical absorption coefficients and electromagnetically induced transparency related to shallow-donor impurity, a two- and three-level approach in the density matrix expansion is used, respectively.

Shallow Donor Impurity States with Excitonic Contribution in GaAs/AlGaAs and CdTe/CdSe Truncated Conical Quantum Dots under Applied Magnetic Field

Using the effective mass approximation in a parabolic two-band model, we studied the effects of the geometrical parameters, on the electron and hole states, in two truncated conical quantum dots: (i) GaAs-(Ga,Al)As in the presence of a shallow donor impurity and under an applied magnetic field and (ii) CdSe–CdTe core–shell type-II quantum dot. For the first system, the impurity position and the applied magnetic field direction were chosen to preserve the system’s azimuthal symmetry. The finite element method obtains the solution of the Schrödinger equations for electron or hole with or without impurity with an adaptive discretization of a triangular mesh. The interaction of the electron and hole states is calculated in a first-order perturbative approximation. This study shows that the magnetic field and donor impurities are relevant factors in the optoelectronic properties of conical quantum dots. Additionally, for the CdSe–CdTe quantum dot, where, again, the axial symmetry is preserved, a switch between direct and indirect exciton is possible to be controlled through geometry.

Pressure and Temperature Effects on the Magnetic Properties of Donor Impurities in a GaAs/AlGaAs Quantum Heterostructure Subjected to a Magnetic Field

The exact diagonalization method has been used to solve the effective-mass Hamiltonian of a single electron confined parabolically in the GaAs/AlGaAs quantum heterostructure, in the presence of a donor impurity and under the effect of an applied uniform magnetic field. The donor impurity is located at distance (d) along the growth direction which is perpendicular to the motion of the electron in a two-dimensional heterostructure layer. We have investigated the dependence of the magnetization (M) and magnetic susceptibility (χ) of a GaAs/AlGaAs quantum heterostructure nanomaterial on the magnetic field strength (ω_c), confining frequency (ω_o), donor impurity position (d), pressure (P) and temperature (T). Keywords: Exact diagonalization, Donor impurity, Magnetic field, Magnetization, Magnetic susceptibility, Pressure and temperature.