Browsing by Author "Fedawy, Mostafa"

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Gate-on-Source TFET Analytical Model: Role of Mobile Charges and Depletion Regions
(Institute of Electrical and Electronics Engineers Inc., 25/10/2021) Eliwy, Mahmoud; Elgamal, Muhammad; Salem, Marwa; Fedawy, Mostafa; Shaker, Ahmed
This study presents a 2-D analytical model for the double gate tunnel FET (DG-TFET). The model considers the gate-on-source overlap that may occur intentionally or unintentionally due to fabrication tolerances. The 2-D Poisson's equation is solved in the main four regions of the structure, namely, the source, channel, drain, and the overlapped region inside the source. The mobile charge inside the channel is taken into consideration. In addition, the source and the drain depletion region lengths are precisely calculated by an iterative technique. Such crucial assumptions and calculations result in accurate expectations of the electrostatic potential. The energy band diagram could be extracted according to the obtained electrostatic potential, and, subsequently, the minimum tunneling width is computed. The impact of channel length and the overlap distance is thoroughly investigated. The results of the proposed model and Silvaco TCAD simulations are compared. The comparison satisfies a good agreement that verifies the validity of the presented model. © 2021 IEEE.
Narrowband Near-Infrared Perovskite/Organic Photodetector: TCAD Numerical Simulation
(Multidisciplinary Digital Publishing Institute (MDPI), 2022-07) Salem, Marwa S; Shaker, Ahmed; Al-Bagawia, Amal H; Aleid, Ghada Mohamed; Othman, Mohamed S; Alshammari, Mohammad T; Fedawy, Mostafa
Narrowband photodetectors (PD) established in the near-infrared (NIR) wavelength range are highly required in a variety of applications including high-quality bioimaging. In this simulation study, we propose a filter-less narrowband PD based on the architecture of perovskite/organic het- erojunction. The most decisive part of the photodetector is the hierarchical configuration of a larger bandgap perovskite material with a thicker film followed by a lower bandgap organic material with a narrower layer. The design of the structure is carried out by TCAD numerical simulations. Our structure is based on an experimentally validated wideband organic PD, which is modified by invok- ing an additional perovskite layer having a tunable bandgap. The main detector device comprises of ITO/perovskite (CsyFA1−yPb(IxBr1−x)3 )/organic blend (PBDTTT-c:C60-PCBM)/PEDOT:PSS/Al. The simulation results show that the proposed heterojunction PD achieves satisfactory performance when the thickness of perovskite and organic layers are 2.5 µm and 500 nm, respectively. The designed photodetector achieves a narrow spectral response at 730 nm with a full width at half-maximum (FWHM) of 33 nm in the detector, while having a responsivity of about 0.12 A/W at zero bias. The presented heterojunction perovskite/organic PD can efficiently detect light in the wavelength range of 700 to 900 nm. These simulation results can be employed to drive the development of filter-less narrowband NIR heterojunction PD.
Numerical analysis and design of high performance HTL-free antimony sulfide solar cells by SCAPS-1D
(Elsevier, 07/12/2021) Salem, Marwa S; Shaker, Ahmed; Othman, Mohamed S; Al-Bagawia, Amal H; Fedawy, Mostafa; Aleid, Ghada Mohamed
Among the various absorbers encountered in thin film solar cells (TFSCs), antimony sulfide (Sb2S3) is considered a suitable candidate as it is a non-toxic and earth-abundant besides its high absorption coefficient. However, some critical issues cause its poor photovoltaic performance. These include unoptimized Sb2S3 layer, interface recombination and cell properties like the ineffective carrier collection and transport. To enhance the power conversion efficiency (PCE) of Sb2S3 solar cell, we suggest some design guidelines by employing device simulation. First, a calibration step is performed vs an experimental arrangement consists of FTO/TiO2/Sb2S3/Spiro-OMeTAD/Au to validate the simulation model. Next, as the organic hole transport material (HTM) often has poor long-term operation stability and demands high-cost fabrication processes, an HTL-free cell is proposed and designed by investigating the impact of the main technological and physical parameters. In the first step in the design of the HTL-free cell, we provide an affinity engineering methodology to tune the conduction band offset between the electron transport layer (ETL) and the absorber. Based on this approach, the most appropriate electron transport material (ETM) is chosen that fulfills the maximum efficiency. Then, an optimization routine is performed to select the most appropriate design parameters and the PCE of the optimized case is found to be about 22%. All simulations, carried out in this work, are performed by SCAPS-1D device simulator under AM1.5G illumination and 300 K temperature.