Magnetic field effect on the binding energy of a hydrogenic impurity in GaAs-Ga₁₋xAlxAs superlattice

The binding energy of shallow hydrogenic impurity in GaAs-GaAs-Ga₁₋xAlxAs superlattices, under the influence of magnetic field, is theoretically studied following a variational procedure within the effective-mass approximation and the new analytic wave function of superlattice. The binding energy is calculed and analyzed for various applied magnetic field, different impurity position and superlattice with different widths. The result show that the impurity binding energy depends strongly on the impurity position and magnetic field. It is also found that for impurities located at the center of the quantum wells of superlattices the binding energy always increases with the applied magnetic field

High Second-Order Nonlinear Susceptibility Induced in GaN/AlxGa1 – xN Coupled Quantum Well for Infrared Photodectors Application

The second harmonic generation (SHG) of GaAs/AlxGa1 − xAs a wurtzite coupled quantum wells (CQWs) is studied theoretically for different widths of well, barrier and values Al concentration, taking into account the strain-induced piezoelectric (PZ) effects. The analytical expression of the SHG susceptibility is deduced by using the compact density matrix approach. The confined wave functions and energies of electrons GaN/AlxGA1 – x N are calculated in the effective-mass approximation, solving the Schrödinger equation by Numerov’s method using six order approximations for the derivatives. The calculated results also reveal that by adjusting the widths of well, the barrier and Al concentration respectively, a set of optimal structural parameters can be found for obtaining a strong SHG susceptibility. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2777

Absorption Coefficients of GaN / AlxGa1 – xN Core-Shell Spherical Quantum Dot

The total absorption coefficient in spherical GaN/AlxGa1 – xN core-shell nanodots is theoretically investigated taking into account effective mass approximation. The influence of the nanosystem geometry upon the energy spectrum and transition energy δE associated to interlevel transitions is studied. We found that the energy transitions vary with the core-shell radius, and the peak position of the total absorption coefficient is greatly affected by changing of the shell radius. The possibility of tuning the resonant energies by using the geometric core shell effect of the spatial confinement can be useful in the optoelectronic devices applications. Also we observed that the magnitudes of the total absorption coefficient can be increased significatly compared traditional cases of QD, and the peaks are shifted to the lower energies. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/2960

Numerical study of electrical characteristics of conjugated polymer light-emitting diodes

Conjugated polymers now provide a class of processible, film-forming semiconductors and metals. In this work, the electronic properties of polymer lightemitting diodes devices are numerically studied. Our results show how an insulating buffer layer with suitable thickness decreases the barrier height at the cathode and therefore increases the electron injection. We also discuss the effects from persistent charged traps

FANO resonances in solid-fluid one and two dimensional systems

The gaol of this paper is to demonstrate that the propagation of acoustic waves in a single slab made of a homogeneous one dimensional (1D) solid embedded in a fluid at oblique incidence on a slab made of two dimensional (2D) rectangular rods immersed in a fluid, can exhibit transmission zeros near resonances the so-called Fano resonances

Nonparabolicity effects on electron-confined LO-phonon scattering rates in GaAs-Al₀.₄₅Ga₀.₅₅As superlattice

We investigate theoretically the effect of nonparabolic band structure on the electron-confined LO-phonon scattering rate in GaAs-Al₀.₄₅Ga₀.₅₅As superlattice. Using the quantum treatment, the new wave function of electron miniband conduction of superlattice and a reformulation of the slab model for the confined LO-phonon modes has been considered. An expression for the scattering rates has been obtained. Our results show that, for transitions related to the emission of confined LO-phonon, the scattering rates are significantly increased in the band nonparabolicity case

Size Effects on Nanowire Phonon Thermal Conductivity: a Numerical Investigation Using the Boltzmann Equation

Analytical solution of the Boltzmann transport equation for phonon transport in Bi$\text{}_{0.95}$Sb$\text{}_{0.05}$ nanowire is obtained. Thermal conductivity was calculated from the analytical solution of the Boltzmann transport equation. We calculate the lattice thermal conductivity of Bi$\text{}_{0.95}$Sb$\text{}_{0.05}$ nanowire as a function of temperature for different wire thicknesses. The results show that thermal conductivity of nanowire can be significantly smaller than the bulk thermal conductivity. We show that low thermal conductivity Bi$\text{}_{0.95}$Sb$\text{}_{0.05}$ nanowire for thermoelectric applications would have a small diameter

Size Effects on Nanowire Phonon Thermal Conductivity: a Numerical Investigation Using the Boltzmann Equation

Analytical solution of the Boltzmann transport equation for phonon transport in Bi0.95Sb0.05 nanowire is obtained. Thermal conductivity was calculated from the analytical solution of the Boltzmann transport equation. We calculate the lattice thermal conductivity of Bi0.95Sb0.05 nanowire as a function of temperature for different wire thicknesses. The results show that thermal conductivity of nanowire can be significantly smaller than the bulk thermal conductivity. We show that low thermal conductivity Bi0.95Sb0.05 nanowire for thermoelectric applications would have a small diameter. PACS numbers: 63.22.+m, 87.15.Aa 1

Theoretical Analysis of Optical Gain in GaN / AlxGa1 – x N Quantum Well Lasers

In this study, we investigated numerically the effect of aluminum concentration, temperature and well width on optical gain GaN / AlxGa1 – xN quantum well lasers, taken into account effective mass approximation. The numerical results clearly show that the increasing of well width, and decreasing of temperature and Aluminum concentration, the optical gain increases

Effects of LO-phonon confinement on electron mobility in GaAs-Al₀.₄₅ Ga₀.₅₅As superlattice

The parallel and perpendicular electron mobilities in a GaAs-Al₀.₄₅ Ga₀.₅₅As superlattice have been calculated. The scattering of electrons by confined longitudinal optical phonons was taken into account. Using the quantum treatment, we offered the new wavefunction of electron miniband conduction in the superlattice as well as reformulation of the slab model for confined LO-phonon modes. An expression for the relaxation time was obtained. Our results show that the relaxation time depends significantly on the total energy of electrons. The effect of the band nonparabolicity on the relaxation time was analyzed. At 300 K, the calculated results reveal that the electron mobility is enhanced when the well width in the superlattice is equal to 45 A