Voltage-dependent Capacitance Research Articles

Floating gate potential of gate-all-around floating gate memory cell: parameter extraction and compact model

The compact modeling of flash memories is crucial for integrated circuit designers to carry out efficient and precise circuit-level evaluations, particularly in the case of 3D NAND flash where the 3D geometry leads to significant parasitic coupling impacts on performance. In this work, we proposed a charge-based modeling approach for gate-all-around floating gate memory cells. The compact model is based on the derived unified charge control model where the mobile charge is explicitly solved. By solving the charge balance model and taking into account voltage-dependent parasitic capacitances for accurate coupling effects, the floating gate potential is accurately computed. The simulation results are validated with numerical TCAD simulation and showed good agreement with TCAD simulation. By solving the charge balance model and considering voltage-dependent parasitic capacitances for more accurate coupling effects, the floating gate potential is accurately calculated. Additionally, the results indicate that subthreshold degradation is caused by interface trap charge in the experimental device, and the proposed model successfully replicates experimental data.

Capacitance Determination for the Evaluation of Electrochemically Active Surface Area in a Catalyst Layer of NiFe-Layered Double Hydroxides for Anion Exchange Membrane Water Electrolyser.

The determination of the electrochemically active surface area (ECSA) of a catalyst layer (CL) of a non-precious metal catalyst is of fundamental importance in optimizing the design of a durable CL for anion exchange membrane (AEM) water electrolysis, but has yet to be developed. Traditional double layer capacitance (Cdl), measured by cyclic voltammetry (CV), is not suitable for the estimation of the ECSA due to the nonconductive nature of Ni-based oxides and hydroxides in the non-Faradaic region. This paper analyses the applicability of electrochemical impedance spectroscopy (EIS) compared to CV in determining capacitances for the estimation of the ECSA of AEM-based CLs in an aqueous KOH electrolyte solution. A porous electrode transmission line (TML) model was employed to obtain the capacitance-voltage dependence from 1.0 V to 1.5 V at 20 mV intervals, covering both non-Faradic and Faradic regions. This allows for the identification of the contribution of a NiFe-layered double hydroxide (LDH) catalyst and supports in a CL, to capacitances in both non-Faradic and Faradic regions. A nearly constant double layer capacitance (Qdl) observed in the non-Faradic region represents the interfaces between catalyst supports and electrolytes. The capacitance determined in the Faradic region by EIS experiences a peak capacitance (QF), which represents the maximum achievable ECSA in an AEMCL during reactions. The EIS method was additionally validated in durability testing. An approximate 30% loss of QF was noted while Qdl remained unchanged following an eight-week test at 1 A/cm2 constant current density, implying that QF, determined by EIS, is sensitive to and therefore suitable for assessing the loss of ECSA. This universal method can provide a reasonable estimate of catalyst utilization and enable the monitoring of catalyst degradation in CLs, in particular in liquid alkaline electrolyte water electrolysis systems.

The Charging and Discharging of Reverse Biased Schottky Diode Voltage-Dependent Capacitor


 Transient analysis of RC circuit with voltage step source, constant resistor and nonlinear voltage-dependent capacitors with the capacitance given by C(vc) = Co/√(1+vc/Vbi), where Co and Vbi are constant and vc is the voltage across the capacitor, was carried out. The analysis was restricted to this class of nonlinear capacitors, because they represent with acceptable approximation the capacitances of reverse-biased Schottky diodes, which are very important and usually used in several static power converters practical applications. The charging and discharging are described by explicitly solvable nonlinear first-order differential equations. The theoretical analysis results are verified by numerical examples with computer simulation and also by experimentation in the laboratory.
 

An Experimental Methodology for Modeling the Voltage-Dependent Capacitance and Resistance of Varistors: Implications on the Estimation of the Power and Energy Dissipation at Low Frequencies

An Experimental Methodology for Modeling the Voltage-Dependent Capacitance and Resistance of Varistors: Implications on the Estimation of the Power and Energy Dissipation at Low Frequencies

Exploring dynamic behaviors of soliton-like pulses in the lossy electrical transmission line model with fractional derivatives: A comparative study

This study aims to explore the intricate behavior of soliton-like pulses within a nonlinear and lossy electrical transmission line. The transmission line is described by a mathematical model called the “beta derivative”, which is specifically designed to characterize the propagation of electrical solitons in media with both nonlinearity and dispersion properties. To achieve this goal, the (G′/G2)-expansion method is applied to a periodically loaded nonlinear beta derivative lossy transmission line with symmetric voltage-dependent capacitances. Soliton-like pulses, including periodic singular, dark, bright, and singular waves, are obtained using the (G′/G2)-expansion method based on the voltage equation. Three-dimensional and two-dimensional graphs of some of the obtained novel solutions satisfying relevant equations are provided to understand the underlying mechanisms of the soliton family. In terms of fractionality, the profiles of dark or bright waveforms maintain their complete forms, but their smoothness increases as the fractional parameters increase. On the other hand, periodic wave solutions exhibit an increase in periodicity. By adjusting the parameters of the model, the characteristics of the waves can be modified to generate desired wave profiles. Additionally, the study involves a comprehensive comparison among solutions derived from models incorporating the beta, conformable, and M−truncated derivatives. It examines how the amplitude of the solitons is influenced by the fractional parameter, utilizing graphs to visualize this impact by assigning specific fractional parameter values. These pulse-like solitons offer promising potential for integration within telecommunication systems, where they can function as information carriers, facilitating heightened data bit rates. By leveraging the findings of this study, advancements in telecommunication technology can be pursued, leading to enhanced efficiency and improved performance.

Supercapacitor’s Parameter Calculation based on Three Branch Equivalent Circuit Model under Different Constant Charging Current

Supercapacitor is a type of energy storage with higher capacitance value compared to the normal capacitor. But it has lower voltage level compared to normal capacitor. However, it can be charged with high current and provide higher current to the load when needed when compared to the same size energy storage such as battery. The Three Branch Equivalent Circuit is one of the simple yet accurate model that has been proposed. The parameter of the Three Branch model included the capacitance, resistance and a unit of voltage dependent capacitance. The Parameter needed to be calculated accurately as it depends heavily on the terminal voltage of the supercapacitor at respective time which obtained through a charging and self-discharging experiment under constant current charging. The different constant charging current give effect toward the parameter calculation as it manipulates the rate of charging and self-discharging. This paper will calculate the parameter of supercapacitor based on the Three Branch model under different constant charging current and compared the result using the simulation to show the accuracy of the model. The parameter obtained throughout the study shows a high accuracy especially the parameters obtained using higher charging current.

Quantitative study the effect of 60Co on S3N4/SO2/Si capacitors via capacitance-voltage model

Two kinds Si3N4/SiO2/Si capacitor were fabricated in this work, firstly. Then the two kinds Si3N4/SiO2/Si capacitors were irradiated by 60Co at five radiation doses level (0, 1·103, 2·103, 3·103, 4·103 Gy(Si)). Because voltage dependent capacitance is the key measurement method in determining the electronic property of microelectronic materials, capacitance-voltage of two kinds Si3N4/SiO2/Si capacitors was measured before and after radiation. To quantitative study the effect of 60Co on S3N4/SO2/Si capacitors, an available capacitance-voltage model was applied to generate theoretical curves of experimental results. The fitting results agree very well with the observed curves (capacitance versus voltage). The quantitative relationship between radiation doses and carrier induced by 60Co on unit area was estimated due to this model is integrable. Another objective of this work was to identify the mathematical relationships between radiation doses and function coefficients corresponding to every experimental curve. Based on the calculation results from the non-linear curve fitting method, the radiation dose-dependent the function coefficient was theoretically explained, successfully. It is also appropriate to use function coefficient which mathematical link radiation dose to the parameters of the model in forecasting experimental C–V before one radiation dose is applied.

Negative Capacitance Phenomenon in GaAs-Based MIS Devices Under Ionizing Radiation

This study focuses on the abnormal peaks observed in voltage-dependent capacitance graphs and negative capacitance behaviors of the GaAs-based MOS devices for the unirradiated sample and after exposing the device to 5 and 10 kGy ionizing (gamma) radiation doses. Experimental results showed that the amplitude of the abnormal peaks, observed at about 1.75 V, increases with the irradiation dose. The peak point was also shifted toward the positive biases after irradiation. Furthermore, the conductance values increased rapidly and reached their maximum level, while the capacitance values reached their minimum level in the high voltage biases. This situation is directly related to the inductive behavior of the MOS devices. However, it has been determined that the MOS device's inductive behavior is more effective after irradiation. These behaviors can be observed because of the ionization process, the MOS device's series resistance, surface states, and due to some displacement damages caused by ionizing radiation. Therefore, the series resistance and the radiation-induced surface states were obtained to clarify the impact of radiation on the device. It was seen that the radiation-induced surface states changed around 3x1012 for the maximum cumulative dose (10 kGy), and the series resistance values changed less than 2 Ω (it was obtained 8.74 Ω for 0 kGy and 6.82 Ω for 10 kGy). As a result, the degradation in the GaAs-based MOS device was determined to be insignificant for 10 kGy doses. Therefore, this MOS device can be safely used as an electronic component in radiation environments such as nuclear plants and satellite systems.

ディスクリートIGBTを用いた電圧共振回路搭載IH調理器の放射EMI対策

The limit levels of radiated EMI for IH cookers were revised to lower values in December 2018 by the Electrical Appliances and Materials Safety Act. In this study, a switching noise mechanism and its countermeasures for an IGBT loaded into a voltage resonance circuit of an IH cooker is analyzed. A device model is developed using a BSIM3 MOSFET model with voltage-dependent capacitors. The inductor and capacitor load switching operation, including the parasitic elements of a test circuit, is simulated, and switching noise generated during turn-off transient conditions is discussed. An effective method for EMI suppression is proposed based on optimization of the C-voltage characteristics and the addition of an external capacitor. The effect of reduced radiated EMI levels is discussed.

Capacitance Variations and Gate Voltage Hysteresis Effects on the Turn-ON Switching Transients Modeling of High-Voltage SiC MOSFETs

This paper presents a discrete and real-time capable dynamic behavioural model of the turn-on switching transition of high-voltage and high-current Silicon Carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET) half-bridge power modules. The dynamic switching model utilizes the Shichman and Hodges equations using voltage-dependent non-linear device capacitances and module electrical parameters to obtain an accurate dynamic model of the device switching transients. The key device states gate-source voltage, drain current and drain-source voltage are modelled. The paper investigates the impact of correct device capacitance modelling with low off-state gate-source voltage values, impacting the device capacitances and causes gate-voltage hysteresis effects. It has been shown that the presented discrete-time dynamic switching model accurately describes the turn-on transient and the results highlight the importance of correct capacitance and threshold voltage characterization data. The modelling results are compared to experimental measurements conducted in a 3.3 kV/750 A SiC MOSFET power module. The model exhibits an average accuracy of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim 4\%$</tex-math></inline-formula> for turn-on energy and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim 1.3\%$</tex-math></inline-formula> for the turn-on time compared to measurements. These models are valuable for rapid and cost effective design and validation of advanced gate-driver circuits and for determining key design and operating parameters such as deadtime, switching frequency and switching losses.

Real-Time FPGA Simulation of High-Voltage Silicon Carbide MOSFETs

This article presents a real-time field-programmable gate array (FPGA)-based dynamic model of high-voltage and high-current silicon carbide (SiC) metal-oxide-semiconductor field-effect transistor ( <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> ) half-bridge power modules. The dynamic switching model utilizes the Shichman and Hodges equations using voltage-dependent nonlinear device capacitances and module electrical parameters to obtain an accurate dynamic model of the device switching transients. The key device states gate-source voltage, drain current, and drain-source voltage are modeled and discretized using forward Euler discrete integration method. Analysis of synthesizing the discrete-time model into real-time FPGA-based system with real-time data output from the on-board digital-to-analog converter is presented in detail. The model is utilized in modeling a 320-kW, medium-voltage dc/dc dual-active bridge converter and verified using dynamic experimental results from a 3.3-kV SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> half-bridge power module. It has been shown that the presented discrete-time dynamic switching model accurately describes the turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> switching transients of the SiC power module at various voltage and current levels. Such models are useful for rapid and cost effective design and prototyping of SiC-based power electronic systems by defining key design and operating parameters, such as deadtime, switching frequency, and switching losses.

Capacitive NO2 Detection Using CVD Graphene-Based Device.

A graphene-based capacitive NO2 sensing device was developed by utilizing the quantum capacitance effect. We have used a graphene field-effect transistor (G-FET) device whose geometrical capacitance is enhanced by incorporating an aluminum back-gate electrode with a naturally oxidized aluminum surface as an insulating layer. When the graphene, the top-side of the device, is exposed to NO2, the quantum capacitance of graphene and, thus, the measured capacitance of the device, changed in accordance with NO2 concentrations ranging from 1-100 parts per million (ppm). The operational principle of the proposed system is also explained with the changes in gate voltage-dependent capacitance of the G-FET exposed to various concentrations of NO2. Further analyses regarding carrier density changes and potential variances under various concentrations of NO2 are also presented to strengthen the argument. The results demonstrate the feasibility of capacitive NO2 sensing using graphene and the operational principle of capacitive NO2 sensing.

Charge transport kinetics in flower like α-MnO2 nano-sheet and α-MnO2 nanowire based supercapacitors

In a supercapacitor, determining the cells’ internal dynamics and limiting factors on the efficiency is essential for device designs. In this context, electrochemical impedance spectroscopy is a powerful tool in investigating device kinetics. This study explained the performance improvement in nanostructured MnO2 electrodes from a diffusion perspective. Firstly, we reported morphological features of flower-like nanosheet MnO2 and nanowire MnO2 with identical crystal structure (α-MnO2 phase) and capacitance-voltage properties. Then, the factors limiting the bias voltage-dependent capacitance efficiency were explained via electrochemical impedance spectroscopy by setting up a three-electrode system. Both resistance and capacitance vs. frequency plots provided important information on ion diffusion and charge transfer mechanisms.

Quantitative Modeling and Analysis of Switching Oscillations of Cascode GaN Devices in Half-Bridge Converters

Having high efficiency and power density, the motor drives based on wide bandgap (WBG) devices can better meet the requirements for developing more electric aircraft (MEA). However, the fast switching characteristic of gallium nitride (GaN) devices has led to undesirable voltage and current oscillations during turn-ON and turn-OFF processes, thus decreasing the reliability of the electric drive system. The complicated structure of cascode GaN devices and various parasitic parameters in the device and the half-bridge converter make the switching oscillation modeling of cascode GaN device comparatively complex. In this article, an equivalent circuit approach in consideration of nonlinear characteristics in voltage-dependent junction capacitances is presented to model the switching oscillation for high-voltage (650 V) cascode GaN-based half-bridge converters. Quantitative mathematical models are derived to provide a theoretical analysis of the switching oscillation for turn-on and turn-off processes of cascode GaN devices. Furthermore, the influences of device and circuit parameters on the oscillation are investigated in detail, offering a reliable guidance to the gate driver and print circuit board design. Finally, experimental studies on the basis of cascode GaN and custom cascodes are carried out to validate the modeling approach. The results have proved that one of the root causes of the oscillations is how the different parasitics interact.

Prediction of overshoot and crosstalk of low‐voltage GaN HEMT using analytical model

Ultra-fast switching speed and low switching loss of the gallium nitride high electron mobility transistors enable the realisation of high power density converter with excellent conversion efficiency. However, the rapid switching transition leads to significant overshoot and crosstalk issues that can degrade the performance of the devices. To facilitate the evaluation of these effects on low-voltage gallium nitride devices, this paper develops an analytical model to predict overshoot and crosstalk during switching transitions accurately and efficiently. The model is constructed based on the detailed circuit deduction of various stages of the device's switching process. It also considers the voltage-dependent junction capacitances as well as the forward and the reverse transconductances. The simulated results obtained from the model are validated experimentally. With the model, the impacts of parasitic elements, especially the power loop inductance, on voltage/current overshoots and spurious voltage due to crosstalk can be easily evaluated, which provides valuable design guidelines for power conversion applications using low-voltage gallium nitride high electron mobility transistor.

On the origin of the turn-on voltage drop of GaN-based current aperture vertical electron transistors

Non-linear output characteristics and the related turn-on voltages of GaN-based current aperture vertical electron transistors (CAVETs) are investigated experimentally. The resistive components are systematically analyzed in dependence of the device layout to determine the dominant resistances in the devices. Current–voltage (IV) and capacitance–voltage-characteristics (CV) are compared to a proposed planar-doped barrier diode (PDBD) model, and the influence of the bound sheet charge density and drift layer carrier concentration is discussed. The observed CV characteristics are in contrast to the PDBD model as a clearly voltage-dependent capacitance was observed and dopant-diffusion forming a p-type aperture was ruled out. Thermionic emission was verified by temperature-dependent IV characteristics indicating interface states causing a potential barrier. Transient drain current measurements revealed a single dominating trap level with an activation energy of EA = 1.086 ± 0.015 eV. This activation energy was attributed to carbon-related acceptor states present at the regrowth interface and the drift layer. Additional test structures revealed that the interface potential barrier and the space charge in the drift layer limit the initial charge transport causing a turn-on voltage in the devices. The results point out the significance of a precise control of the regrowth interface properties and the effective carrier density in the drift layer to enable efficient, high-power devices based on the CAVET technology.

A Nonlinear Model Based Analysis and Accurate Design of Ultracapacitor Stack for Energy Storage Systems

Sizing of widely deployed ultracapacitor stack is an essential requirement in design of energy storage systems. Unlike a linear capacitor that displays constant capacitance, UCs exhibit considerable nonlinearity in the form of voltage-dependent capacitance and notable variation in characteristics during operation. Analyzing the behavior of overall UC bank that consists of several stacked nonlinear UC cells and evaluating its effective capacitance is therefore critical. In this paper, an exact-analysis framework is presented for characterizing the nonlinear behavior of the overall UC stack. Closed-form expressions for stacks effective capacitance, terminal voltage characteristics, and stored energy are derived as a function of unit cell nonlinear parameters and number of cells, using which deviations in stack behavior from linear characteristics are analytically captured. It is shown that the resultant stack of existing method will either be over-sized and expensive, or insufficient to meet ESS specifications in practice. To address these limitations, an improved stack design method is proposed based on the nonlinear UC model, which optimizes the size of UC stack and guarantees that the ESS specifications are accurately met. Experimental results on two UC stack hardware prototypes validate the accuracy of proposed nonlinear analysis and the improved design method for ride-through applications.

Investigation of Trap States, Series Resistance and Diode Parameters in Al/Gelatin/n-Si Schottky Diode by Voltage and Frequency Dependent Capacitance and Conductance Analysis

Inorganic-organic Schottky contacts based on Gelatin on n-Si wafer have been prepared by a spin coating technique. The reverse and forward bias capacitance-voltage () and conductance-voltage () properties of the Al/Gelatin/n-Si Schottky diode at room temperature in the frequency range from 30 kHz to 1 MHz have been computed by taking into account the series resistance () and interface states () effects. The conductance and Hill-Coleman method were used to determine interfacial layer capacitance (), and The values of and were determined as 810 Ω and 1.52 x−1012 eV−1 cm−2 for 30 kHz and 38 Ω and 3.38 x 1011 eV−1 cm−2 for 1 MHz. Experimental results corroborated that the and are influential parameters which severely impact the basic electrical parameters of Al/Gelatin/n-Si Schottky diode. Both the measured capacitance () and conductance () were corrected in order to obtain the real diode capacitance () and conductance (). Schottky diode parameters such as barrier height (), ionized donor density (), Fermi level (), built-in voltage () were extracted from the frequency-dependent and relations. The values of was determined as 0.796 eV for 30 kHz and 1.090 eV for 1 MHz. The and values were observed to decrease, while the values increase as the frequency increases. Results reveal that the fabricated diode can potentially be used as a promising candidate material for electronics applications.

Measurement Uncertainty in Voltage Coefficients for Compressed-Gas Capacitor Based on a Simplified Tilting Method

High-voltage compressed-gas capacitor is a type of precision equipment commonly used in high voltage laboratories. The voltage dependence of capacitance, in other words, the voltage coefficient of capacitance, is an important factor to ensure the measurement accuracy of capacitors. The simplified tilting method derived from PTB, which provides a solution for measuring the voltage coefficient of the high-voltage capacitor with compressed-gas coaxial cylindrical electrodes structure. However, it is not an easy work for most laboratories. In order to evaluate the voltage coefficient based on the simplified tilting method, a special experimental platform was developed. The high-voltage capacitor installed on the platform can be tilted and rotated at high voltage and be remote-controlled. Base on the developed platform, the voltage coefficient of a 350 kV high-voltage capacitor was measured. In order to verify, it was re-measured by the direct measurement method with a dummy high-voltage capacitor, and before that, the voltage coefficient of the dummy capacitor was calibrated with a near zero-voltage-coefficient capacitor. The results show a good agreement, the consistency of the measurement results is better than 1.2&#x00D7;10^-6 between the two methods. Furthermore, the evaluation of measurement uncertainty in the voltage coefficient determination of capacitor based on simplified tilting method is introduced in detail. The evaluation results show that the expanded uncertainty is significantly better than 2.0&#x00D7;10^-6, k=2.

Tunable and Miniaturized Microwave Filters Using Carbon Nanotube-Based Variable Capacitors

In this paper, we introduce a novel concept of tunable and miniaturized filtersthat embed, as voltage-controlled elements, state-of-the-art variable capacitors, based on vertically aligned carbon nanotubes (VACNTs). Starting from a theoretical estimation of the voltage-dependent capacitance between two adjacent CNTs, we extended this physics principle to a large matrix of CNTs, suitably placed on the molybdenum electrodes of an interdigitatedcapacitor (IDC), since molybdenum can withstand the high temperature necessary in the plasma process for the growth of the VACNTs. The IDC is the tunable element of a microwave filter, which must fulfill the need for both reconfigurability (being either a low-pass, a high-pass, or a band-pass filter, at discretion) and low-voltage frequency tuning of reflection&#x002F;transmission coefficients. For all these reasons, a very compact layout made of T-type cells (comprising VACNT-based variable capacitors and distributed inductors) was designed, simulated, fabricated, and tested, targeting the C, X, and K_u bands (4&#x2013;16 GHz) for wireless and radar applications. Taking as a reference the free-space wavelength <i>&#x03BB;</i>₀ at 10 GHz, the band-pass filter has overall dimensions of just 3.19 mm &#x00D7; 3.47 mm (i.e., 0.11<i>&#x03BB;</i>₀ &#x00D7; 0.12<i>&#x03BB;</i>₀), with the minimum of the reflection coefficient shifting of 1.16 GHz (within the X band) for an applied dc bias voltage of just 4 V and spanning between &#x2212;24.81 dB and &#x2212;36.13 dB. Furthermore, the maximum rejection is 31.65 dB, and the 3-dB fractional bandwidth is 12.44&#x0025;. The proposed filters are the proof that nanomaterials can be profitably integrated into microwave components for next-generation transceivers.