Electronic band structure of GaAs/AlxGa1−xAs superlattice in an intense laser field

ABSTRACT: We perform theoretical calculations for the band structure of semiconductor superlattice under intense high-frequency laser field. In the frame of the non-perturbative approach, the laser effects are included via laser-dressed potential. Results reveal that an intense laser field creates an additional geometric confinement on the electronic states. Numerical results show that when tuning the strength of the laser field significant changes come in the electronic energy levels and density of states

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

ABSTRACT: 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

Intersubband transitions in an asymmetric double quantum well

The intersubband optical absorption in an asymmetric double quantum well for different barrier widths and the right well widths are theoretically calculated within the framework of effective mass approximation. The results obtained show that the intersubband transitions and the energy levels in an asymmetric double quantum well can be importantly modified and controlled by the barrier width and the well width. The sensitivity to the barrier and well widths of the absorption coefficient can be used in various optical semiconductor device applications. (c) 2006 Elsevier Ltd. All rights reserved

The Effect of the Electron Temperature on Incompressible Strips in Quantum Hall Regime

We used a theory of thermo-hydrodynamics in quantum Hall system observed on a two-dimensional system in high magnetic fields at low temperatures, to investigate the electron temperature in the linear response regime. The variation of electron temperature exhibits an antisymmetric distribution of the incompressible strips. According to this result, we obtain effects of the electron temperature on the current density distribution using a Thomas-Fermi-Poisson approximation. We observe that incompressible strips change with increasing and/or decreasing the electron temperature with regard to the lattice temperature. DOI: 10.12693/APhysPolA.123.31

The variation of electronic properties with the doping concentration of modulation-doped AlxGa1-xAs-GaAs double quantum wells

In this paper we have calculated the sub-band structure and the confinement potential of modulation-doped Ga1-xAlxAs-GaAs double quantum wells as a function of the doping concentration. The electronic properties of this structure were determined by self-consistent solutions of the Schrodinger and Poisson equations. To understand the effects of doping concentration on band bending, sub-band energies, and sub-band populations, the doping concentration on one right side of the structure is decreased while holding it constant on the left side. We found that at low doping concentrations on the right side, the effects of the doping concentration are more pronounced on band bending and sub-band populations. (c) 2006 Elsevier Ltd. All rights reserved

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 Ga (x) In1 - x N (y) As1 - 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 - x In (x) N (y) As1 - 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

Pediatric Mass Lesions of the Head and Neck Region and Fine-Needle Aspiration Biopsy Results

Objective: 1. To provide a classification of pediatric mass of the head and neck region and evaluate their frequency. 2. To examine the findings of fine-needle aspiration biopsy (FNAB) in pediatric patients along with its contribution to diagnosis. Methods: Totally, 233 pediatric patients (125 boys and 108 girls) operated at Baskent University for head and neck mass were included. Clinical, radiological, and histopathological data were retrieved from medical records. Results: The mean age was 119 +/- 65 months, and the mean duration of follow-up was 75 +/- 49 months. Localization of the masses was as follows: 208 (89%) in the neck, 21 (9%) in the oral cavity, 2 (1%) in the neck and nasopharynx, and two (1%) in the larynx. The most common surgical procedure was open excisional biopsy (n=105, 45%) followed by cystic mass excision (n=72, 31%) and salivary gland excision (n=33, 14%). Basedon histopathological findings, benign cystic lesions were the most common disease group (n=77, 33.1%), whereas reactive lymphadenopathy was the most common condition (n=36, 15%) when a single disease was considered. Infectious/inflammatory diseases, malignancies, and benign salivary glands were present in 49 (21%), 24 (10.3%), and 22 (9.4%) patients, respectively. FNAB was performed in 29.8% of the patients with an accuracy of 90.3% (95% CI, 80.1-96.4). Conclusion: The differential diagnosis of head and neck masses during childhood includes a wide spectrum with the different conditions being benign cystic diseases of congenital origin and reactive lymphadenopathies. Owing to its high predictive value, FNAB represents a rapid and reliable method that can be commonly used in both adult and pediatric patients