A surface-potential based drain current model for short-channel symmetric double-gate junctionless transistor

Junctionless transistors, which do not have any pn junction in the source-channel-drain path have become an attractive candidate in sub-20 nm regime. They have homogeneous and uniform doping in source-channel-drain region. Despite some similarities with conventional MOSFETs, the charge-potential relationship is quite different in a junctionless transistor, due to its different operational principle. In this report, models for potential and drain current are formulated for shorter channel symmetric double-gate junctionless transistor (DGJLT). The potential model is derived from two dimensional Poisson’s equation using “variable separation technique”. The developed model captures the physics in all regions of device operation i.e., depletion to accumulation region without any fitting parameter. The model is valid for a range of channel doping concentrations, channel thickness and channel length. Threshold voltage and drain-induced barrier lowering values are extracted from the potential model. The model is in good agreement with professional TCAD simulation results.     

A transmission line model for metallic carbon nanotube interconnects

A transmission line (TL) model describing the propagation of electric signals along metallic single wall carbon nanotube (CNT) interconnects is derived in a simple and self‐consistent way within the framework of the classical electrodynamics. The conduction electrons of metallic CNTs are modelled as an infinitesimally thin cylindrical layer of a compressible charged fluid with friction, moving in a uniform neutralizing background. The dynamic of the electron fluid is studied by means of the linearized hydrodynamic equations with the pressure assumed to be that of a degenerate spin‐½ ideal Fermi gas. Transport effects due to the electron inertia, quantum fluid pressure and electron scattering with the ion lattice significantly influence the propagation features of the TL. The simplicity and robustness of the fluid model make the derivation of the TL equations more straightforward than other derivations recently proposed in the literature and provide simple and clear definitions of the per unit length (p.u.l.) TL parameters. In particular, this approach has provided a new circuit model that can be used effectively in the analysis of networks composed of CNT transmission lines and lumped elements. The differences and similarities between the proposed model and those given in the literature are highlighted. Copyright © 2006 John Wiley & Sons, Ltd.     

Electronic model of a Ferroelectric Field Effect transistor

Abstract

A pair of electronic models has been developed of a Ferroelectric Field Effect transistor. These models can be used in standard electrical circuit simulation programs to simulate the main characteristics of the FFET. The models use the Schmitt trigger circuit as a basis for their design. One model uses bipolar junction transistors and one uses MOSFET's. Each model has the main characteristics of the FFET, which are the current hysterisis with different gate voltages and decay of the drain current when the gate voltage is off. The drain current from each model has similar values to an actual FFET that was measured experimentally. The input and output resistance in the models are also similar to that of the FFET. The models are valid for all frequencies below RF levels. Each model can be used to design circuits using FFET's with standard electrical simulation packages. These circuits can be used in designing non-volatile memory circuits and logic circuits and are compatible with all SPICE based circuit analysis programs. The models consist of only standard electrical components, such as BJT's, MOSFET's, diodes, resistors, and capacitors. Each model is compared to the experimental data measured from an actual FFET.     

An analytic drain current model for long‐channel undoped gate stack surrounding‐gate MOSFETs including interface fixed charges

On the basis of the exact solution of Poisson's equation and Pao–Sah double integral for long‐channel bulk MOSFETs, a continuous and analytic drain current model for the undoped gate stack (GS) surrounding‐gate (SRG) metal–oxide–semiconductor field‐effect transistor (MOSFET) including positive or negative interface fixed charges near the drain junction is presented. Considering the effect of the interface fixed charges on the flat‐band voltage and the electron mobility, the model, which is expressed with the surface and body center potentials evaluated at the source and drain ends, describes the drain current from linear region to saturation region through a single continuous expression. It is found that the surface and body center potentials are increased/decreased in the case of positive/negative interface fixed charges, respectively, and the positive/negative interface fixed charges can decrease/increase the drain current. The model agrees well with the 3D numerical simulations and can be efficiently used to explore the effects of interface fixed charges on the drain current of the gate stack surrounding‐gate MOSFETs of the charge‐trapped memory device. Copyright © 2013 John Wiley & Sons, Ltd.     

A drain avalanche hot carrier lifetime model for n- and p-channel MOSFETs

A simple and physical drain avalanche hot carrier lifetime model has been proposed. The model is based on a mechanism of interface trap generation caused by recombination of hot electrons and hot holes. The lifetime is modeled as /spl tau/(I/sub d//W)/sup 2//spl prop/(I/sub sub//I/sub d/)/sup -m/. The formula is different from the conventional /spl tau/I/sub d//W-I/sub sub//I/sub d/ model in that the exponent of I/sub d//W is 2, which results from the assumed mechanism of the two-carrier recombination. It is shown that the mechanism gives a physical basis of the empirical /spl tau/-I/sub sub//W model for NMOSFETs. The proposed model has been validated experimentally both for NMOSFETs and for PMOSFETs. Model parameters extracted from experimental data show that carrier critical energies for creating damage are lower than the interface potential barriers. It is supposed that oxide band edge tailing enables low-energy carriers to create the damage. The channel hot electron condition becomes the worst case in short channel NMOSFETs, because gate voltage dependence of the maximum channel electric field decreases.     

A simple method to fabricate high-performance carbon nanotube field emitters

A simple new method to fabricate carbon nanotube field emitters was developed. Single wall carbon nanotubes with high graphitization were attached on Sn or Ni layered glass substrate in-situ in arc-discharge chamber. Post heat treatments below the deformation temperature of soda-lime glass guaranteed a good mechanical adhesion and electrical contact of the nanotubes. The morphology of the metal electrode layers was examined with the heat treatment temperatures to optimize the heat treatments. The emitters formed on Sn layers showed lower turn-on voltage and higher current density than those formed on Ni layers. A good field emission performance was realized in an emitter where nanotubes were deposited on Sn layer of the thickness 100 nm and annealed at 300^∘C. The current density was 2.5 mA/cm² at 3.5 V/μm. The emitter structure was maintained stable for 8 h.     

Simulation of top-contact pentacene thin film transistor

In this paper we present both finite element based and analytic model simulations of pentacene based organic thin film transistor. The finite element type simulation is done using Silvaco’s Atlas simulator and the analytic model simulation is performed using a Matlab code based on the standard transistor equations. Both the Atlas and Matlab simulations agree approximately with the published experimental result. The results of the simulations show a current ratio of 2.11×10⁶ for Atlas and 1.8×10⁷ for Matlab simulations. The threshold voltage extracted from the finite element type simulation is 1.1 V which is in good agreement with 1.2 V used for Matlab simulation. However, the contact resistance shows a quite significant variation between the two simulation mechanisms. The finite element type simulation gives a contact resistance of 10 kΩ whereas the Matlab simulation predicts a contact resistance 1.9 kΩ.     

Improved PMSM model considering flux characteristics for model predictive‐based current control

Model predictive‐based current control, which was proposed in our previous study, offers better current response performance by employing mathematical models of an inverter and a permanent magnet synchronous motor (PMSM). The performance of this kind of approach depends on the predictive model. From a more practical point of view, current behavior in the steady state should be improved. In our previous model predictive‐based current control, the inverter model was refined by taking the dead‐time into consideration. The use of the refined inverter model reduces the current offset in the control. However, the PMSM model was not investigated. This paper proposes a more appropriate PMSM model for model predictive‐based current control in order to improve the current prediction in the steady state. For the purpose, we incorporate more detailed magnetic flux characteristics instead of average characteristics into the improved PMSM model. Specifically, in the improved PMSM model, the inductance of the PMSM is divided into transient and steady‐state parts on the basis of magnetic saturation. The effectiveness of the improved model in the model predictive‐based current control is demonstrated through simulations and experiments. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Current and voltage excitations for the eddy current model

We present a systematic study of how to take into account external excitation in the eddy current model. Emphasis is put on mathematically sound variational formulations and on lumped parameter excitation through prescribed currents and voltages. We distinguish between local excitation at known contacts, known generator current distributions and non‐local variants that rely on topological concepts. The latter case entails the violation of Faraday's law at so‐called cuts and prevents us from reconstructing a meaningful electric field. Copyright © 2004 John Wiley & Sons, Ltd.     

A 1D numerical model for rapid stress analysis in bipolar junction transistors

Stress effects in semiconductor devices have gained significant attention in semiconductor industry in recent years, and numerical modeling is often used as a powerful tool for stress analysis in semiconductor devices. Here, we present a nontraditional 1D model for fast stress analysis in bipolar junction transistors. Because bipolar transistors are operationally 1D devices, it is possible to speed up the simulation with a 1D numerical model and get results that are comparable with 2D and 3D simulation outcomes. This model consists of a complete numerical algorithm that can be used for stress analysis of bipolar transistors on any plane. Existing 1D simulators take more time as they solve all device equations throughout the device. In contrast, our model optimizes the solutions for different regions with the development and inclusion of specific algorithms. A fractional starting point is introduced for the depletion region to speed up the process further. This way, faster computing time and much higher accuracy can be reached. At the same time, popular 2D and 3D simulators, which are using finite element methods, are naturally much slower, especially if high accuracy is needed. Simulation results of this 1D model match well with the simulation results of a 2D model developed with a commercial technology computer aided design (TCAD) tool. The validity of our model was verified with experimental results and theoretical expectations as well. Copyright © 2016 John Wiley & Sons, Ltd.     

A calculation model for cathodic protection of underground extensive structures using impressed current cable anodes

 Proper design of cathodic protection by use of impressed current cable anodes requires the knowledge of current and potential distribution along the anode and the structure to be protected. The conductive coupling between these earth-return circuits results in different current and potential distributions along both structures when comparing with the case of separate anode. In the paper calculation models – accurate and simplified – are presented. In the accurate model an interchange of currents flowing along both structures is taken into account, whereas in the simplified method the structures are treated as separate earth return circuits. The formulas are derived for calculation of such parameters as longitudinal current, protective current density, potential to the remote earth and potential to the adjacent earth. Calculations have been carried out in which the influence of the distance between the two structures on the values and distribution of currents and potentials along the anode and the protected structure has been examined. The relations presented may be useful at design stage of impressed current cathodic protection systems containing cable anodes. Received: 15 February 2001/Accepted: 15 March 2001     

变面积式电涡流传感器线圈阻抗理论计算模型

变面积式电涡流传感器相比于传统的变距式传电涡流感器具有线性度好和量程易扩展等优点。介绍了变面积式电涡流传感器的基本测量原理和理论模型的建立方法。该模型利用二阶矢量位结合截取边界法建立了相关电磁场方程组,在此基础上推导并建立了传感器的理论模型并给出了传感器线圈阻抗计算以及相关场量的闭合解析表达式。实验结果证明了此模型的有效性和正确性,该计算模型与传统的数值仿真运算相比,不仅物理意义明晰,而且极大缩短了运算时间。     

异步电机转子IGBT斩波调阻调速的准动态模型

转子斩波调阻是异步电机的一种简便有效的调速方法，本文提出了一种新型的采用IGBT作斩波管的具有吸收保护作用的斩波回路拓扑结构，并对该系统整流回路的准动态过程进行了详细研究，推导出斩波管占空比与等效电阻之间的非线性函数关系，给出了外接电阻阻值的选择方法。     

涡流刹车控制系统的故障成因与解决

详细介绍了7838刹车、控制单元和易烧模块产生的原因及解决的措施,同时强调要保证单元的完好性,实际应用中应重视安装工艺。     

双极性电堆中漏电电流简化计算模型

在试验基础上,定性分析了各因素对漏电电流的影响;在解释漏电电流产生机理的同时,提出简化计算模型,并通过试验对模型进行了验证.得到结论如下:在支路电阻R较大时,单体数为N的双极性电堆,第n个单体的漏电电流jn=(N-2n+1)E/2R;第n个单体和第n+1个单体间的电流损耗为:ln=(nN- n2)E/2R(n＜N).     

混合电极电流密度分布的数值模型

根据Bulter-Volumer和Fick定律建立了一维的LiCoO2/LiMn2O4混合(材料)电极的数值模型.基于模型,研究了两种材料在恒电流充放电过程中的电流密度分布,并计算了粒度、组分含量、倍率对其电流密度分布的影响.计算结果表明,恒电流充放电情况下,两种材料的电流密度分布不均一:单一组分最大电流密度值随粒度和倍率的增大而增大,随含量的增大而减小.在放电初期和末期,电流主要分布在LiCoO2上,而在充电的初期和末期,电流主要分布在LiMn2O4上.     

Small-signal modelling for time-length compensation algorithm in current controlled converters

A unified small-signal modeling method is proposed for current controlled converters using discrete-time analysis method. The relationship between the controlled current and the duty ratio is performed by discrete-time analysis which automatically incorporates the sample-and-hold effect. The proposed small-signal mode is accurate when the modulation frequency varies from zero to half the switching frequency. It is very easy to apply the proposed model to all current controlled converters. When an amplitude peak in the current-loop gain is observed at half the switching frequency, subharmonic oscillation can be predicted. Based on the proposed model, a time-length compensation algorithm for elimination of subharmonic oscillation can be analyzed while other small-signal modeling methods cannot be applied in this condition. Simulations and experiments are committed to verify the analysis.     

NPC结构型SVG的模型预测电流控制策略

针对中点钳位型(neutral point clamped,NPC)的静止无功发生器(static var generator,SVG),提出了一种模型预测电流控制策略.由于SVG的预测模型实际上是一种开环模型,故其交流侧实际输出电流与指令电流存在电流跟踪误差,在平衡计算量与跟踪精度的前提下,设计了电流跟踪精度误差的评...     

三相电流型PWM整流器改进型模型预测控制

模型预测控制算法是以系统模型为基础,通过优化性能指标获得最优控制量的一种新型算法,具有很好的控制性能,已经获得广泛的应用。针对三相电流型PWM整流器,本文提出了一种改进型模型预测控制。根据电流型PWM整流器在dq0旋转坐标系下的数学方程,建立了增量式预测控制模型;根据系统控制要求设计了控制器的优化性能指标,性能指标综合考虑了系统误差和控制增量的影响,通过求解优化性能指标得到预测控制增量表达式。实验结果表明,该控制算法具有很好的控制性能。相比于传统的PI调节器,该控制方法参数易整定,且具有很好的阻尼特性。