Emine Ozturk

The electric field effects on intersubband optical absorption of Si δ-doped GaAs layer

The intersubband transitions in Si δ-doped GaAs structures is theoretically investigated for different applied electric fields. For an uniform distribution the electronic structure has been calculated by solving the Schrodinger and Poisson equations self-consistently. From our calculations, it is found that the subband energies and intersubband optical absorption is quite sensitive to the applied electric field. This gives a new degree of freedom in various device applications based on the intersubband transitions of electrons.

Intersubband transitions for single, double and triple Si δ-doped GaAs layers

The intersubband transitions in single, double and triple Si δ-doped GaAs structures are theoretically studied for different applied electric fields. Electronic properties such as the confining potential, the subband energies and the eigen envelope wave functions have been calculated by solving the Schrodinger and Poisson equations self-consistently. We have seen that the intersubband transitions are very sensitive to the type of structure and are dependent on the applied electric field. The electric field and structure dependence of the intersubband optical absorption is interesting for potential device applications in a class of photodetectors and optical modulators.

Si δ-doped GaAs structure with different dopant distribution models

We have theoretically investigated the diffusion of donor impurities of single Si δ-doped GaAs inserted into a quantum well at T=0 K. The spread of the impurities is taken into account in three different models: (i) a uniform distribution, (ii) a triangular distribution and (iii) a nonuniform distribution. In this article, the nonuniform distribution is different from the Gaussian distribution used by other authors. The electronic structures were calculated by solving the Schrodinger and Poisson equations self-consistently. We also found the confining potential, the charge density, the subband energies, the subband occupations and the Fermi energy. In this study, we have seen that the electronic structures are quite sensitive to the type of donor distribution when the thickness of the donor distribution (Δz) is large.

Effect of Magnetic Field on a p-Type δ-Doped GaAs Layer

The energy levels of holes in a p-type ?-doped GaAs structure under a magnetic field are theoretically calculated within the framework of the effective mass approximation for a uniform acceptor distribution. The electronic structure is calculated by solving the Schr?dinger and Poisson equations self-consistently. The effect of the magnetic field on the potential profile changes the degree of the confinement and localization, and thus this behavior can be used to study these systems in regions of interest, without the need to grow many different samples. It is found that the heavy-hole subbands contain many more energy states than the light-hole ones; the population of the heavy-hole levels represents approximately 91% of all the carriers without magnetic field. With increasing magnetic field the total population of the heavy-holes increases and the number of filled states changes.

Electronic properties of Si δ-doped GaAs under an applied electric field

We have theoretically investigated the electronic structure of Si δ-doped GaAs inserted into a quantum well under an applied electric field. For uniform distribution we have studied the influence of the electric field on the donor concentration. The electronic properties such as the effective potential, the density profile, the subband energies, the subband occupations and the Fermi energy level have been calculated by solving the Schrodinger and Poisson equations self-consistently. From our calculations, we have seen that the change of the electronic properties as dependent on the applied electric field is more pronounced at low doping concentration. The high electric fields can induce a spatial separation between confined electrons and ionized dopants in the δ-doped GaAs structure, resulting in enhanced free-carrier mobility in devices.

INTERSUBBAND OPTICAL ABSORPTION IN QUANTUM WELLS UNDER APPLIED ELECTRIC AND INTENSE LASER FIELDS

Within the framework of the effective mass approximation, we have theoretically investigated the linear intersubband optical absorption in a quantum well under external electric and intense laser field. Results obtained show that intersubband optical transition and energy levels in quantum wells can significantly be modified and controlled by the electric field and intense laser field. Generally there is a distinct feature for the case of the intersubband absorption compared with intersubband optical absorption in a quantum well with an applied electric field.

Resonant peaks of the linear optical absorption and rectification coefficients in GaAs/GaAlAs quantum well: Combined effects of intense laser, electric and magnetic fields

In this study, the resonant peaks of the linear optical absorption (OA) and rectification coefficients in GaAs/GaAlAs quantum well are calculated as dependent on the applied electric field (F), the magnetic field (B) and the laser field intensity parameter (α0). Our results show that the shape of confined potential profile, the energy levels and the dipole moment matrix elements are changed as dependent on the F, B and α0. Also, the resonant peaks of the OA and rectification coefficients depend on the applied external field effects. Therefore, the variation of the resonant peaks of these coefficients which can be appropriate for various optical modulators and infrared optical device applications can be smoothly obtained by the alteration electric, magnetic and intense laser field.

Nonlinear Intersubband Transitions in Square and Graded Quantum Wells Modulated by Intense Laser Field

The intersubband optical absorption coefficients and the refractive index change depending on the intense laser field (ILF); both are calculated in a square quantum well (SQW) and a graded quantum well (GQW). Our results show that the position and the magnitude of the linear, nonlinear and total absorption coefficients and refractive index changes depend on the laser field parameter and the quantum well (QW) shape. By increasing the ILF value, we can obtain a red shift or a blue shift in the intersubband optical transitions as dependent on the shape of the QW. For the SQW, the intersubband absorption spectrum shows a blue shift up to the critical laser field value. This spectrum shows a red shift for ILF values larger than this certain value. For the GQW, the intersubband absorption spectrum shows a red shift by increasing the ILF. Thus the absorption coefficients and the refractive index changes, which can be suitable for great performance optical modulators and multiple infrared optical device applications, can be easily obtained by tuning the ILF value and the QW shape.

Intersubband Transitions of Si δ-Doped GaAs Layer for Different Donor Distribution Models

For different donor distribution types we theoretically investigate the intersubband transitions of single Si δ-doped GaAs structure as dependent on the applied electric field. The diffusion of donor impurities is taken into account in two different models: a triangular distribution and a non-uniform distribution. The electronic properties such as the effective δ-potential, the subband energies and the eigen-envelope wavefunctions have been calculated by solving the Schrodinger and Poisson equations self-consistently. Abrupt changes of the subband energy difference and the absorption peak are realized whenever the applied electric field reaches a certain value. These critical electric field values change dependent on the donor distribution model. The intersubband absorption spectrum shows that redshifts appear up to the critical electric field value for the (1–2) and (1–3) intersubband transitions. This spectrum also shows that blueshifts can occur when the electric fields are higher than certain values. These changing intersubband absorption peaks can be used in various infrared optical device applications.

Interband transitions dependent on indium concentration in Ga1−xInxAs/GaAs asymmetric triple quantum wells

In this paper, the optical and electronic properties of asymmetric triple quantum well (ATQW) structures are studied depending on the indium concentrations while quantum well (QW) thicknesses and b...