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An analytical model of a pair-interacting electron gas localized in an asymmetric biconvex strongly oblate lens-shaped GaAs quantum dot has been considered. The wave functions and the energy spectrum of the system have been calculated in the frame of the exactly solvable two-dimensional Moshinsky model. The character of long-wavelength transitions between the center of mass levels of the system have been obtained when the generalized Kohn's theorem is realized. [ABSTRACT FROM AUTHOR]

The resistance of a monolayer of complexes of the double-stranded DNA with quantum dots were computed. It was shown that with the non-competitive DNA hybridization and in the presence of monovalent positively charged ligands in the solution, a decrease in resistance occurs as compared to that for uncharged ligands. It is shown that the charged ligands enhance the sensitivity of the DNA chips as compared to the uncharged ones. [ABSTRACT FROM AUTHOR]

Electronic states are considered in a cylindrical quantum dot with the Kratzer confining potential in the axial direction. In this system, the nonlinear optical rectification and second harmonic generation for intraband transitions are studied theoretically. Analytical expressions are calculated for the energy spectrum of the wave functions, as well as for the matrix elements. The dependences of the coefficients of the optical rectification and the second harmonic on the incident photon energy are obtained. The nonmonotonic behavior of the dependences of the peaks heights of the optical rectification coefficients depending on the half width and depth of the Kratzer confining potential in the axial direction is demonstrated. [ABSTRACT FROM AUTHOR]

The single-particle states of charge carriers in the nanospherical InP/InAs/InP heterostructure are theoretically considered in the isotropic effective mass approximation and in the regime of strong size quantization. The results of numerical computations of the energy levels of charge carriers at various thicknesses of the quantizing of the InAs layer of the indicated heterophase structure are presented. It is shown that it is possible to achieve the desired value and position of the size quantization levels of charge carriers in the layer by an appropriate choice of the layer thickness. The interband optical transitions in the InAs layer are also considered. The values of the effective broadening of the band gap of the InAs layer as a function of the layer thickness are computed. By numerical computations, it is shown that the absorption has a resonant character and that the diagonal transitions dominate in the spectrum of the interband absorption. For several diagonal transitions involving both light and heavy holes, the values of threshold frequencies and absorption curves are given. In the spherical InP/InAs/InP nanoheterostructure, the photoluminescence spectra were also constructed for various temperatures close to room temperature. [ABSTRACT FROM AUTHOR]

Within the approximation of an isotropic effective mass, the one-particle states of charge carriers in the layered CdS/HgS/CdS heterostructure are considered. It is shown that under conditions in which the strong-quantization regime is realized in the HgS layer, the spatial localization of charge carriers is realized there with the maximum probability. The energy spectrum and envelopes of the wave functions of the electron and hole states are computed in the structure under consideration. The interband optical absorption is computed, when the system is a layered cylindrical quantum dot and when there is a free motion of the charge carriers along the symmetry axis. For the same cases, the photoluminescence spectrum is also considered. [ABSTRACT FROM AUTHOR]

An adiabatic method is presented for solving a boundary discrete spectrum problem for a parabolic quantum well and a rectangular quantum well with infinitely-high walls in the presence of a hydrogen-like impurity. The upper and lower bounds for the energy of the ground state of the systems are obtained under the conditions of the shift of the Coulomb center in a given range of the parameter with respect to earlier variational estimates. The comparison of the rate of convergence of the adiabatic expansion of the solution in parametric bases in the cylindrical and spherical coordinates is carried out. [ABSTRACT FROM AUTHOR]

Within the framework of adiabatic approximation, the energy levels and direct interband light absorption in a strongly prolated ellipsoidal quantum dot are studied. Analytical expressions for the particle energy spectrum and absorption threshold frequencies in three regimes of quantization are obtained. Selection rules for quantum transitions are revealed. Absorption edge and absorption coefficient for three regimes of size quantization (SQ) are also considered. To facilitate the comparison of obtained results with the probable experimental data, size dispersion distribution of growing quantum dots by the small semiaxe in the regimes of strong and weak SQ by two experimentally realizing distribution functions have been taken into account. Distribution functions of Lifshits–Slezov and Gaussian have been considered. [ABSTRACT FROM AUTHOR]

The absorption of light in an ensemble of non-interacting cylindrical quantum dots in the presence of a magnetic field is discussed using a model consisting of dots with rectangular infinitely-high potential barriers. The ensemble’s absorption coefficient is calculated — as well as the threshold frequency of absorption — as a function of the applied magnetic field and the quantum dot size. Theoretical results are compared with experimental data on magneto-luminescence in an In0.53Ga0.47As/InP cylindrical quantum dot system. In addition, using a perturbation theory framework, the influence of excitonic effects on the behaviour of the electron-hole energetic spectrum of said system is discussed. [ABSTRACT FROM AUTHOR]

Interband transitions in a narrow-gap InSb cylindrical quantum dot (QD) have been theoretically studied in the regime of strong dimensional quantization with allowance for a nonparabolic dispersion of electrons and light holes. The corresponding absorption coefficients and threshold frequencies for a QD array are calculated within the framework of a two-band Kane model for electrons and light holes and a parabolic dispersion law for heavy holes. These threshold frequencies fall in the IR range. Quantitative calculations are performed using the recent data of Moiseev et al. [1] on the growth of InSb quantum dots by liquid phase epitaxy. [ABSTRACT FROM AUTHOR]

Direct optical absorption of light is theoretically investigated in a spherical quantum dot from GaAs. The confinement potential of the dot is approximated as parabolic. Three regimes of size quantization are discussed: weak, strong, and intermediate. The corresponding threshold frequencies of absorption are determined. A comparison with the case of a spherical quantum dot with rectangular infinitely high confinement potential is performed.© 2005 Pleiades Publishing, Inc. [ABSTRACT FROM AUTHOR]