Papers by Keyword: Electric Field

Abstract: This study investigates the influence of active cell geometry on the static performance of 10-kV 4H-Silicon Carbide (SiC) Junction Barrier Schottky (JBS) diodes. Two types of diodes were fabricated and characterized, one with a hexagonal cell and the other with a stripe cell. While forward conduction characteristics were comparable, the reverse leakage current of the hexagonal cell was more than two orders of magnitude lower than that of the stripe cell at 8 kV. 3D TCAD simulations revealed that this discrepancy stems from strong electric field concentrations both at the bottom corners of the P⁺ junctions and at the center of the Schottky contact in the stripe structure. These localized fields reduce the Schottky barrier height and enhance electron injection. In contrast, the hexagonal cell exhibited a more uniform electric field distribution in both regions, effectively suppressing leakage current. These findings underscore the critical role of active cell geometry in achieving robust reverse blocking performance in ultra-high-voltage SiC JBS diodes by clarifying the physical mechanisms contributing to leakage current behavior.

Abstract: The aim of this study is to investigate the overcurrent turn-off robustness limit of SiC MOSFETs from three different manufacturers with three different cell technologies up to very high turn-off currents to determine a possible destruction limit and failure type. The influence of the negative gate-source voltage (V_GS,off) was studied because of the high drain-source overvoltage in connection with the decreased V_GS,off, which is the most critical point for the gate oxide field stress for the different cell technologies. All measurements were performed at a positive gate-source voltage (V_GS,on) above the specified datasheet values to reach high currents without channel pinch-off. In addition, the influence of temperature on the overcurrent robustness was studied. Finally, TCAD simulations were performed to determine the reason for the failure mechanism under the overcurrent turn-off conditions. All the manufacturer devices can withstand several times higher gate-source voltages under overcurrent conditions than the values recommended in the datasheet.

Abstract: A theoretical study of the effect of applying a lateral electric field on type I and type II GaAs/AlGaAs quantum ring with different Al concentration in the barrier is presented. The effect on the quantum states of the carriers was investigated using the approximation of the effective mass. It’s showed that the electric field has a great effect on the wavefunction and the energy of the carriers. The transition point of the quantum ring from type I to type II was found with increasing electric field strength. For electric fields less than 4.75 x 10^-4 V/cm, the quantum ring is of type II: the symmetry of electron ground state is X. Above this threshold, it transitions to type I : the symmetry of electron ground state is Γ. Also, the effects of electric field on the linear and non-linear optical properties of the studied structure illuminated with different incident optical intensity were studied. There is an increase in the radiative lifetime with a notable decrease in the absorption coefficient and the refractive index with the increase in the intensity of the electric field. It’s noted that the increase in the type II quantum ring lifetime (20%) is greater than that of type I quantum ring (10 %) due to the confinement of the G-electron in the quantum ring which is not the case with the X-electron. To the best of our knowledge, this article is the first theoretical study of the influence of lateral electric field on physical properties of type II GaAs/AlGaAs quantum ring structures.

Abstract: In this paper, a new method for solving Maxwell's equations associated with electrostatic separators is presented. The boundary value problem is transformed into an optimization problem by using the finite element method. Numerical simulations were carried out using Matlab software that performs equation-based multiphysics modeling for different physical processes by applying the finite element method and modified method of characteristics to a system of partial differential equations. The finite-element method is used to solve Poisson's equation, and a modified method of characteristics is used to satisfy the current continuity condition. The two methods are repeated to obtain a consistent solution to the described equations. The simulation model has been developed to determine the influence of the electrical conductor, semiconductor, and dielectric particles on the important parameters of the corona mechanism, namely the distribution of electric potential, electric field, current density, space charge density, and collection efficiency.

Abstract: A mathematical model of diffraction of electromagnetic microwaves on explosive materials with different physical and electromagnetic parameters has been developed. The model was constructed by solving Maxwell's equation for two surfaces separating three dielectric materials, in particular air, explosive material, and the substrate on which the explosive material is located. Different types of soil and wood are considered as the substrate material, which meets the conditions for demining large areas of the locality. The results of the numerical calculation showed that 67 % to 92 % of the energy of electromagnetic radiation is concentrated in the explosive material. In this case, trinitrotoluene, which is placed on dry sand, has the highest absorption rates, while wet wood, due to its high coefficient of dielectric permittivity, successfully transmits electromagnetic microwaves through its surface. The obtained models and numerical results are considered as theoretical basis for predicting the effectiveness of remote methods of detection and disposal of explosive materials using electromagnetic microwaves. The obtained results showed that this method will be least effective for explosive materials placed on wet wood. In this case, the lowest reflection coefficient is observed that complicates the search for explosive material and the lowest absorption coefficient that complicates the artificial detonation of explosive material due to its heating under the influence of electromagnetic microwaves.

Abstract: This research paper investigates the application of a Double Gate (DG) Tunnel Field-Effect Transistor (DG-TFET) for the detection of cell lines derived from breast cancer tissue, namely Hs578T, MDA-MB-231, MCF-7, and T47D. The device incorporates two nanocavities positioned beneath the two gate electrodes, significantly enhancing detection capabilities. The study emphasizes the differentiation between healthy non-tumorigenic cells (MCF-10A) and breast cancer-derived cell lines by incorporating gate engineering into the TFET. Furthermore, the research explores the impact of changes in dielectric values specific to different breast malignant cell types on the biosensor's detection capabilities. Additionally, the investigation delves into the influence of variations in device geometry, including cavity dimensions and dielectric layer thickness, on critical parameters such as drain current sensitivity, transconductance sensitivity, and ION/IOFF sensitivity. Sensitivity analysis concerns drive current, ION/IOFF ratio, threshold voltage (Vth), and transconductance. The structural design of the device is tailored to facilitate array-based diagnosis and screening of cell lines derived from breast cancer tissue. This design offers several advantages, including a simplified transduction process, compatibility with CMOS processes, cost-effectiveness, reproducibility, and adjustable electrical responses. The researchers employed ATLAS, a two-dimensional (2D) device simulator from Silvaco, to model and define the device structure. The numerical simulations validate the device's performance, demonstrating favorable ON-OFF transition profiles.

Abstract: In this study, we have examined, under the influence of an electric field applied along the z-direction, the binding energy Stark-shift, the dipole moment and the polarizability of a confined shallow donor impurity in GaAs conical-shaped quantum dots (CSQD). With square infinite confinement system, the calculations are based on the approximation of the effective mass by using the finite difference method. Our results show that increasing the radius of the CSQD structure and the electric field intensity increases the Stark shift binding energy and it has a mixed behavior as a function of the impurity position. Furthermore, the polarizability and the dipole moment vary in a quasi-linear way as a function of the dot radius and they follow a decreasing function as a function of the electric field intensity. These two physical parameters have a double behavior, they decrease with the position of the impurity in the strong confinement regime and they increase in the top regions of the quantum dot. These results provide a lot of information about the behavior of the electronic wave function which give more interesting ideas for the fabrication of optoelectronic devices.

Abstract: Analytical expressions are obtained for the wave functions and the energy spectrum of charge carriers in the β-HgS nanolayer of a cylindrical core/shell/shell β-CdS/ β-HgS/ β-CdS nanocomposite in the presence of a strong lateral uniform electrostatic field. It is shown that, under the influence of an external field, the position of the chemical potential of the electron-hole subsystem at absolute zero shifts to the bottom of the conduction band of the sample. The displacement value is determined by the intensity of the external field and increases linearly with increasing field. The concentration, internal energy, and heat capacity of the electronic subsystem of the β-HgS layer in the presence of a field are compared with similar values in the absence of a field. Calculations show that under identical conditions, the presence of an external field leads to an increase in the carrier concentration, which in turn leads to an increase in the internal energy and heat capacity of the system of electrons and holes in the layer.

Abstract: The study is concerned with the effects of slip velocity on a non-uniform rotating electroosmotic flow in a micro-channel. Electroosmotic driven fluid flow is obtained by the application of a potential electric field which describes the nonlinear Poisson-Boltzmann equation. The external electric potential is applied along the x and y directions which provides the necessary driving force for the electroosmotic flow. Two semi analytical techniques were employed to obtain the solution of the nonlinear Poisson-Boltzmann equation. The first method incorporates the complex normalized function into the Laplace transform and the second method is the combination of the Laplace transform and D’Alembert technique. Further, the complex normalized function became difficult to invert in closed form, hence we resort to the use of numerical procedure based on the Stehfest's algorithm. The graphical solutions to the axial velocities on both x and y components have been obtained and analyzed for the effects of the slip parameter and the amplitude of oscillation of the micro-channel walls. The solutions show that the rotating electroosmotic flow profile and the flow rate greatly depend on time, rotating parameter and the electrokinetic width. The results also indicate that the applied electric field and the electroosmotic force, play vital role on the velocity distribution in the micro-channel. The fact is that the solutions obtained in this study synthesize most of the solutions available in the previous studies. Finally, this study will be relevant in biological applications particularly in pumping mechanism to help transport substances within different parts of the systems.

Abstract: The addition of energy from the electric field is one way in the active method to overcome the nucleation barriers of inorganic phase change materials (PCM) e.g. salt hydrate. The effort is to aim at improving the performance of PCM as a thermal energy storage system. Moreover, the passive method commonly uses a chemical substance called nucleator agent to induce the nucleation and to reduce the phase separation that typically occurs during the freezing-thawing cycle of salt hydrate PCM. In this paper, we report an experimental study to conduct the effect of the static electric field (DC voltage) and nucleator agent as a combination of passive and active methods on the nucleation of salt hydrates consisting of CaCl₂·6H₂O and Ca(NO₃)₂·4H₂O. In general, the nucleation temperature of CaCl₂·6H₂O and CaCl₂·6H₂O+BaSO₄ (0.1 wt%) become higher with the increase of the intensity of the electric field, leading to the decreases of supercooling degree. Besides that, the electric field also induces the increase in the nucleation rate, as measured by the shorter induction time. Meanwhile, the case for Ca(NO₃)₂·4H₂O and Ca(NO₃)₂·4H₂O+Ba(OH)₂·8H₂O (1 wt%) show that the nucleation temperature tends to become smaller with increase the intensity of the electric field, leading to increases the supercooling degree. However, the addition of the nucleator agent, Ba(OH)₂·8H₂O (1 wt%) to Ca(NO₃)₂·4H₂O has not provided a significant result in terms of nucleation probability.