F. Ungan

The effect of magnetic field on the impurity binding energy of shallow donor impurities in a Ga1−xInxNyAs1−y/GaAs quantum well

Using a variational approach, we have investigated the effects of the magnetic field, the impurity position, and the nitrogen and indium concentrations on impurity binding energy in a Ga1−xInxNyAs1−y/GaAs quantum well. Our calculations have revealed the dependence of impurity binding on the applied magnetic field, the impurity position, and the nitrogen and indium concentrations.

OPTICAL INTERSUBBAND TRANSITIONS AND BINDING ENERGIES OF DONOR IMPURITIES IN Ga1-xInxNyAs1-y/GaAs/Al0.3Ga0.7As QUANTUM WELL UNDER THE ELECTRIC FIELD

The effects of nitrogen and indium mole concentration on the intersubband optical absorption for (1–2) transition and the binding energy of the shallow-donor impurities in a Ga1-xInxNyAs1-y/GaAs/Al0.3Ga0.7As quantum well under the electric field is theoretically calculated within the framework of the effective-mass approximation. Results are obtained for several concentrations of nitrogen and indium, and the applied electric field. The numerical results show that the intersubband transitions and the impurity binding energy strongly depend on the nitrogen and indium concentrations.

Effects of an Intense Laser Field and Hydrostatic Pressure on the Intersubband Transitions and Binding Energy of Shallow Donor Impurities in a Quantum Well

We have calculated the intersubband transitions and the ground-state binding energies of a hydrogenic donor impurity in a quantum well in the presence of a high-frequency laser field and hydrostatic pressure. The calculations are performed within the effective mass approximation, using a variational method. We conclude that the laser field amplitude and the hydrostatic pressure provide an important effect on the electronic and optical properties of the quantum wells. According to the results obtained from the present work, it is deduced that (i) the binding energies of donor impurity decrease as the laser field increase, (ii) the binding energies of donor impurity increase as the hydrostatic pressure increase, (iii) the intersubband absorption coefficients shift toward lower energies as the hydrostatic pressure increases, (iv) the magnitude of absorption coefficients decrease and also shift toward higher energies as the laser field increase. It is hopeful that the obtained results will provide important improvements in device applications.

Effects of an intense, high-frequency laser field on bound states in Ga1 − xInxNyAs1 − y/GaAs double quantum well

Within the envelope function approach and the effective-mass approximation, we have investigated theoretically the effect of an intense, high-frequency laser field on the bound states in a GaxIn1 − xNyAs1 − y/GaAs double quantum well for different nitrogen and indium mole concentrations. The laser-dressed potential, bound states, and squared wave functions related to these bound states in Ga1 − xInxNyAs1 − y/GaAs double quantum well are investigated as a function of the position and laser-dressing parameter. Our numerical results show that both intense laser field and nitrogen (indium) incorporation into the GaInNAs have strong influences on carrier localization.

THE EFFECTS OF TEMPERATURE AND HYDROSTATIC PRESSURE ON THE DIAMAGNETIC SUSCEPTIBILITY OF A DONOR IN A QUANTUM WELL

Using the effective-mass approximation within a variational scheme, we have calculated the diamagnetic susceptibility and binding energy of a hydrogenic donor in a quantum well under different temperatures and hydrostatic pressure conditions. Our calculation have revealed the dependence of the diamagnetic susceptibility and the impurity binding on temperature and hydrostatic pressure.

Nonlinear optical properties of asymmetric double-graded quantum wells

ABSTRACT In this work, the effects of the structure parameters, such as the central barrier thickness and the aluminium concentrations x, on the linear and nonlinear intersubband optical absorption coefficients and refractive index changes of the asymmetric double-graded quantum wells (ADGQWs) under the presence of an external static electric field are studied theoretically. The nonlinear optical properties of the ADGQWs are obtained using the compact-density matrix approach and iterative method. The numerical results obtained from the present work show that the external static electric field and the structure parameters play an important role in the optical properties of ADGQWs. Depending on the asymmetric nature of the confinement potential, in an electric field of  kV/cm, the overlap between electronic wave functions decreases with increasing field whereas it increases for larger field values. The tunability of intersubband transitions can be applied to optical modulators and various device applications based on the optical transitions of electrons.

Infrared transitions between hydrogenic states in GaInNAs/GaAs quantum wells

The effects of nitrogen and indium concentrations on the 1s, 2s, 2p0 and 2p±-like donor impurity energy states in a single Ga1−xInxNyAs1−y/GaAs quantum well (QW) are investigated by variational approach within the effective mass approximation. The results are presented as a function of the well width and the donor impurity position. It is found that the impurity binding and transition energies depend strongly on the indium concentration while depends weakly on the nitrogen concentration.

ELECTRONIC STRUCTURE AND BAND BENDING OF MODULATION-DOPED GaAs/Alx Ga1-xAs SYMMETRIC AND ASYMMETRIC DOUBLE QUANTUM WELLS UNDER AN APPLIED ELECTRIC FIELD

In this study, we have calculated theoretically the effects of the electric field and doping concentration on the sub-band energies, the electron population, and total charge density in modulation-doped symmetric and asymmetric GaAs/Al0.33Ga0.67As double quantum wells. Electronic properties of the system are determined by the solving the Schrodinger and Poisson equations self-consistently in the effective-mass approximation. The application of an electric field in the growth direction of the system causes a polarization of the carrier distribution and shifts the sub-band energies, which may be used to control and modulate intensity output devices. In an asymmetric double-quantum-well structure, the effects mentioned above appear more clearly.