Yazar "Arraoui, R." seçeneğine göre listele

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    Central-cell corrections for hydrogenic, silicon (Si), selenium (Se), sulfur (S), and germanium (Ge) donor impurities and pressure-temperature effects on the optical properties of the GaAs/GaAlAs multi-layer quantum disk
    (Elsevier, 2024) Fakkahi, A.; Başer, Pınar; Jaouane, M.; Sali, A.; Ed-Dahmouny, A.; El-Bakkari, K.; Arraoui, R.
    GaAs/GaAlAs quantum dots can be doped with various impurities to modify their optoelectronic properties. Common impurities used for doping include: Hydrogenic impurity (HI), Silicon (Si), Selenium (Se), Germanium (Ge), and Sulfur (S) are common n-type dopant in GaAs-based materials. This work has investigated the effects of temperature and pressure on the refractive index changes (RICs) and optical absorption coefficients (OACs) in the multi-layer quantum disk, accounting for central cell correction. We have used the finite element method to calculate the eigenvalues and their corresponding wave-functions. These values are utilized in the computation of the OACs and RICs. Our outcomes can be summarized as follows: (i) The applied pressure induces a red-shift of the OACs peaks, and their magnitude is reduced. Similarly, temperature causes a blueshift of the OACs peaks, and their magnitude is enhanced. (ii) The presence and type of impurity lead to significant changes in both OACs and RICs.
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    The effects of temperature and pressure on the optical properties of a donor impurity in ?In; Ga?N=GaN multilayer cylindrical quantum dots
    (2022) Jaouane, M.; Sali, A.; Fakkahi, A; Arraoui, R.; Ungan, Fatih
    This paper examines the variation of the linear, third-order nonlinear and total intersubband optical absorption (refractive index changes) coefficients of a donor impurity in multilayer cylindrical quantum dots (MCQDs), under the effect of temperature T and hydrostatic pressure P. Moreover, in this study, we also examined the effect of structure parameters on the optical absorption coefficients of the system. The Schr€odinger equation describing the system is solved numerically by the finite element method (FEM) within the effective mass approximation. In our calculations, the confinement potential is modeled by a parabolic form in the radial direction and a square one in the z-direction. The optical absorption coefficients and refractive index changes have been investigated versus the quantum dot radius, indium composition and intensity of the incident electromagnetic for three allowed transitions: 1s - 1p, 2s - 1p and 1p - 1d. Our essential outcomes exhibit that the optical absorption coefficients and refractive index changes are strongly sensitive to the variation of quantum dot sizes, which enhance and blueshift as the quantum confinement is strong. On the contrary, the optical absorption coefficients and refractive index changes diminish and redshift as the quantum confinement reduces.
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    Hydrogenic donor-related binding energy and diamagnetic susceptibility in multilayer cylindrical quantum dots under hydrostatic pressure
    (Springer Heidelberg, 2023) El-Bakkari, K.; Jaouane, M.; Fakkahi, A.; Ed-Dahmouny, A.; Arraoui, R.; Azmi, H.; Sali, A.
    This study employs the finite element method based on the effective-mass approximation (EMA) to numerically investigate the behavior of impurities in multilayer cylindrical quantum dots (MLCQDs). We consider the applied hydrostatic pressure (P) in our numerical analysis. The study presents numerical results for macroscopic parameters that follow the electronic properties, the binding energy (E-b), and diamagnetic susceptibility (?(dia)) of the ground state (1 s) and some excited states (1p and 2 s) of the impurity in the MLCQDs. The E-b and the ?(dia) for the three states are calculated as a function of the radius R, impurity position z0 and the hydrostatic pressure. The numerical results show that the binding energies of impurities decrease with the radius for all levels. The E-b(1s) and E-b(1p) have three maximum values that typify the number of the quantum dot layer materials contained in our system. Moreover, the diamagnetic susceptibility for the three levels is strongly affected by the hydrostatic pressure, impurity location, and radius.
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    Investigation of nonlinear optical rectification within multilayer wurtzite InGaN/GaN cylindrical quantum dots under the impact of temperature and pressure
    (Elsevier, 2024) Jaouane, M.; Ed-Dahmouny, A.; Fakkahi, A.; Arraoui, R.; El-Bakkari, K.; Azmi, H.; Sali, A.
    We have looked numerically at variations of the nonlinear optical rectification (NOR) for an impurity donor localized in a wurtzite Inx0Ga1-x0N/GaN multilayer cylindrical quantum dots (MLCQDs), which is under the effect of hydrostatic pressure and temperature. Using the effective mass approximation, the compact density matrix formalism, we have solved the Schrodinger equation by the finite element method (FEniCS Project) . Firstly, we consider the impact of altering the polarization direction of the incident electromagnetic radiation. Specifically, we explore two distinct scenarios: axial, along the growth axis of the structure, and circular, across the cross-section of the cylinder. From our investigation, we found that the nonlinear optical rectification is determined by two main parameters: the transition energy, which is mainly related to quantum confinement, and the geometrical factor that depends on the distribution of the electron wave functions. The NOR experiences a blueshift with an increase in hydrostatic pressure or indium composition, and a redshift with an increase in temperature or quantum dot radius, where the impurity is located in the center of the upper QD. Furthermore, the results show that the amplitude and resonance peak position of NOR are significantly influenced by varying the impurity's position and the barrier width.
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    Modeling and simulation of the influence of quantum dots density on solar cell properties
    (Springer Heidelberg, 2023) Jaouane, M.; Fakkahi, A.; Ed-Dahmouny, A.; El-Bakkari, K.; Tuzemen, A. Turker; Arraoui, R.; Sali, A.
    Based on the finite element method using the FEniCS computing platform and python programming, we solve the Schrodinger equation within the effective mass approximation. Its solution gives us the necessary energy for an electron to transit from an intermediate band to a conduction band, as well as the distribution of probability density within the system. In this work, we have investigated the efficiency of the InAs/GaAs pyramid quantum dot intermediate band solar cell (PQD-IBSC) as a function of the structure parameters and quantum dot density. The simulation results indicated the strong dependence of the efficiency of PQD-IBSC on the confinement effect, quantum dot number or quantum dot density and coupling strength. The conversion efficiency grows from 14.4587% to the optimal efficiency 17.8807%. Generally, the best efficiency is obtained for small barrier width, large quantum dot height and great quantum dot density.
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    Optical and electronic properties of confined exciton in a dot-in-rod structure
    (Elsevier Ltd, 2025) Jaouane, M.; Arraoui, R.; Ed-Dahmouny, A.; Fakkahi, A.; Azmi, H.; El-Bakkari, K.; Althib, H.M.
    This study explores the excitonic properties of CdSe/CdS dot-in-rod nanostructures using the perturbation method within the effective mass approximation, combined with the finite element method. We analyze the first three excitonic energy levels (1S, 2S, and 3S), along with the electron and hole states, the exciton binding energy, and absorption coefficient for transitions between these levels under an applied electric field, as functions of the dot radius (Rc) and sidewall thickness (C). Our results reveal that the exciton binding energy reaches a maximum at a critical dot radius (Rc≃2nm), while excitonic energy levels decrease with increasing R due to quantum confinement effects. The applied electric field significantly modifies the exciton energy, increasing the first and third states while decreasing the second due to the quantum-confined Stark effect, which induces carrier polarization. The absorption coefficient for transitions among the 1S, 2S, and 3S peaks in an energy range comparable to experimentally observed photoluminescence spectra. Additionally, as Rc increases, the absorption peak undergoes a blue shift, whereas an increase in C results in a redshift and a slight enhancement in amplitude. These findings highlight the potential for tuning excitonic properties in optoelectronic and quantum applications. © 2025 Elsevier Ltd
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    Photoionization cross section of donor single dopant in multilayer quantum dots under pressure and temperature effects
    (2022) Jaouane, M.; Sali, A.; Fakkahi, A; Arraoui, R.; Ed-Dahmouny, A.; Ungan, Fatih
    The shallow donor single dopant confined in the multilayer cylindrical quantum dots is investigated numerically within the framework of effective-mass approximation. The Schr¨odinger equation that governs the wave function of a complicated system is solved numerically by the finite element method using the Python programming language. The results indicate that the photoionization cross section (PCS) is similar to the Gauss function curve, the height of the curve’s peak is proportional to oscillator strength, and the center peak position is related to the impurity binding energy. These two last parameters are dependent on the distribution of probability density across each part of the system. The probability density is tuned by the electron confinement and optical transition. The augmentation of dot radius or temperature decreases the electron confinement, which causes a redshift of PCS, and the presence of hydrostatic pressure blue shifts the PCS. On the other side, As the dot radius and hydrostatic pressure are increased, the oscillator’s strength increases, raising values near the critical energy, and vice versa for temperature.
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    The effects of temperature and pressure on the optical properties of a donor impurity in (In, Ga)N/GaN multilayer cylindrical dots
    (Academic Press Ltd- Elsevier Science Ltd, 2022) Jaouane, M.; Sali, A.; Fakkahi, A.; Arraoui, R.; Ungan, F.
    This paper examines the variation of the linear, third-order nonlinear and total intersubband optical absorption (refractive index changes) coefficients of a donor impurity in multilayer cylindrical quantum dots (MCQDs), under the effect of temperature T and hydrostatic pressure P. Moreover, in this study, we also examined the effect of structure parameters on the optical absorption coefficients of the system. The Schrodinger equation describing the system is solved numerically by the finite element method (FEM) within the effective mass approximation. In our calculations, the confinement potential is modeled by a parabolic form in the radial direction and a square one in the z-direction. The optical absorption coefficients and refractive index changes have been investigated versus the quantum dot radius, indium composition and intensity of the incident electromagnetic for three allowed transitions: 1s - 1p, 2s - 1p and 1p - 1d. Our essential outcomes exhibit that the optical absorption coefficients and refractive index changes are strongly sensitive to the variation of quantum dot sizes, which enhance and blueshift as the quantum confinement is strong. On the contrary, the optical absorption coefficients and refractive index changes diminish and redshift as the quantum confinement reduces.