Engineering model of a biased metal–molecule–metal junction

Molecular electronic devices show promise for future applications, but assessment of their utility is limited by the lack of physically based engineering models. In this paper, quantum-mechanical results obtained with density-functional theory (DFT) are used as a starting point to construct an efficient device-level model of a prototype molecular electronic device consisting of a metal/benzene-1,4-dithiolate/metal junction. This model is based on a physically transparent analytical expression with a few parameters that are fitted to DFT results and experimental data. We demonstrate that the model describes the I–V characteristics of the device accurately and is computationally efficient for implementation within a circuit simulator.     

Insulated gate bipolar transistor (IGBT) modeling using IG-SPICE

A physics-based model for the insulated gate bipolar transistor (IGBT) is implemented into the widely available circuit simulation package IG-SPICE. Based on analytical equations describing the semiconductor-physics, the model accurately describes the nonlinear junction capacitances, moving boundaries, recombination, and carrier scattering, and effectively predicts the device conductivity modulation. In this paper, the procedure used to incorporate the model into IG-SPICE and various methods necessary to ensure convergence are described. The effectiveness of the SPICE-based IGBT model is demonstrated by investigating the static and dynamic current sharing of paralleled IGBTs with different device model parameters. The simulation results are verified by comparison with experimental results     

Simulation Model of a Direct-Current Electric Locomotive with Commutator Traction Motors

A dc electric locomotive simulation model is considered that makes it possible to study transient and steady processes and may serve as a basis for the notion of a “digital locomotive” being implemented within the “Digital Railway” project. One of the most popular electric locomotives is selected, which is designed for pulling freight trains along long-distance railways electrified with direct current with a voltage of 3000 V. The electric locomotive model is based on a mathematical model of a collector traction engine. The model takes into account the nonlinearity of the main pole’s magnetic characteristic, as well as the effect of eddy currents in solid magnetic circuit sections on the magnetic flux variation. The model provides a mechanism for regulating motors in the course of investigations in accordance with operating conditions. The processes of resistor starting and voltage regulation by connection to resistors by means of transposition, as well as motor regulation by changing the magnetic flux, are taken into account. The possibility of using the developed model to study the traction substation–traction network–electric rolling stock system, which is determined by different operating modes of the traction network in the process of converting electrical energy into mechanical, is shown. Calculations of various locomotive operating modes in the event of failure in the contact network are carried out.     

A new two-dimensional analytical subthreshold behavior model for submicron Triple Material Gate (TM) GaN MESFET

A new two-dimensional (2D) analytical model for a Triple Material Gate (TM) GaN MESFET has been proposed and modeled to suppress the short channel effects and improve the subthreshold behavior. The analytical model is based on a two-dimensional analysis of the channel potential, threshold voltage and subthreshold swing factor for TM GaN MESFET is developed. The aim of this work is to demonstrate the improved subthreshold electrical performances exhibited by TM GaN MESFET over dual material gate and conventional single material gate MESFET. The results so obtained are verified and validated by the good agreement found with the 2D numerical simulations using the ATLAS device simulation software. The models developed in this paper will be very helpful to understand the device behavior in subthreshold regime for future circuit applications.     

Modeling and measurement of the wavelength-dependent output properties of quantum-well optical amplifiers: effects of a carrier-dependent escape time

We present a model for quantum-well (QW) semiconductor optical amplifiers (SOAs) that considers bidirectional field propagation and the carrier densities in the barrier and QW regions. Carrier capture from the barriers into the QWs and carrier escape from the QWs to the barriers are included by means of effective capture and escape times. The model incorporates the wavelength dependence of the optical response of the active region and the effects of spectral hole burning via an analytical approximation to the susceptibility of the active material, which allows one to very effectively include the wavelength dependence of the output properties of the SOA. The model is used to analyze the experimental results obtained for a multiquantum-well SOA. The simulations results show a good agreement with the experimental data when a carrier-density dependent escape time from the QW to the barrier regions is considered.     

Line current spectrum analysis in saturated three-phase cage induction machines

The paper deals with modeling of saturated induction machines aimed at current signature analysis. The numerical model takes into account saturation of the main magnetic flux path using the concept of the air-gap permeance modulation. The modified winding function theory is applied in order to calculate all the winding inductances in the machine. An alternative method for calculation of mutual stator–rotor inductance, which avoids the need for using two-dimensional look-up tables is proposed. The proposed approach significantly simplifies the implementation of the already complex model. Derived analytical expressions for self and mutual inductances of the rotor loops, as well as their derivatives, additionally simplify model implementation. The results from numerical model are experimentally verified. Experimental results confirm presence of all of the harmonics predicted by the model.     

新型整流桥串并联切换直流融冰装置

我国南方地区冬季气温低湿度高,在远距离传输的高压输电线路上经常出现区域覆冰问题,覆冰严重时会造成杆塔倒塌等电力事故,本文研究的新型整流桥串并联切换直流融冰装置即用于解决输电线路覆冰问题,避免造成大面积供电中断。本文基于常规十二脉动直流融冰装置,通过原理分析、参数设计和仿真验证提出一种新型直流融冰拓扑,可以同时满足导线融冰的大电流和地线融冰的高电压需求。相比于常规十二脉动直流融冰装置,采用新型直流融冰拓扑可以选用一半容量的换流变压器和一半电流定额的晶闸管,显著降低设备成本;在大电流输出模式下可以有效减小注入系统的谐波电流,从而减小接入点的系统电压畸变。本文研究的新型整流桥串并联切换直流融冰装置有利于降低直流融冰装置的设备投资成本,同时改善直流融冰装置投入运行时的系统电压质量。关键词：线路覆冰;直流融冰装置;串并联切换;切换刀闸;平衡电抗器;成本优势中图分类号：TM755     

Transient analysis of multi‐state dc–dc converters using system energy characteristics

The study of multi‐state dc–dc power conversion techniques is restricted by the complicated inner switching behaviors. This paper presents a general and unified transient analysis for various sorts of multi‐state dc–dc converters from a viewpoint of their system energy characteristics. With the applications to the boost converters, the proposed analytical method has indicated its advantages of high convenience and practicability to the multi‐state converters. The generalized concepts of system energy parameters of dc–dc converters are introduced and applied to the transient analysis. Consequently, the expressions of system model parameters of multi‐state dc–dc converters are deduced. The new 2nd order transfer functions are obtained to describe the large‐ and small‐signal mathematical models accurately. The model simulation and experimental results are provided to support the theoretical analysis. Copyright © 2007 John Wiley & Sons, Ltd.     

Input and intrinsic device modeling of VCSELs

An efficient model scheme that combines the non-linear behavior of the input parasitics with the intrinsic fundamental device rate equations of the Vertical Cavity Surface Emitting Lasers (VCSELs) is proposed. A systematic methodology for the model parameter extraction from dc and ac, electrical and optical measurements, is also presented and simulation results are compared with the experimental measurements. Extraction and simulation procedures are implemented in commercial integrated circuit design tools and they are proved to be very fast while they preserve adequate accuracy.     

Modeling of peak voltage and current of nanowire resonant tunneling devices: case study on InAs/InP double‐barrier heterostructures

In this paper, we develop an analytical model for the prediction of the peak voltage and the current in the current–voltage characteristics of nanowire resonant tunneling heterostructures. The model is applied in the case study of double‐barrier InAs/InP devices, and the results are obtained from numerical carrier transport calculations, in terms of structural parameters such as the nanowire radius as well as the width of the barriers and quantum well. Copyright © 2013 John Wiley & Sons, Ltd.     

3D analytical modeling of surface potential,threshold voltage,and subthreshold swing in dual-material-gate (DMG) SOI FinFETs

Here, we develop a 3D analytical model for potential in a lightly doped dual-material-gate FinFET in the subthreshold region. The model is based on the perimeter-weighted sum of a dual-material double-gate (DMDG) asymmetric MOSFET and a DMDG symmetric MOSFET. The potential model is used to determine the minimum surface potential needed to obtain the threshold voltage \((V_{\mathrm{T}})\) and subthreshold swing (SS) by considering the source barrier changes in the leakiest channel path. The proposed model is capable of reducing the drain-induced barrier lowering (DIBL) as well as the hot carrier effects offered by this device. The impact of control gate ratio and work function difference between the two metal gates on \(V_{\mathrm{T}}\) and SS are also correctly established by the model. All model derivations are validated by comparing the results with technology computer-aided design (TCAD) simulation data.     

Analytical modeling of threshold voltage for symmetrical silicon nano-tube field-effect-transistors (Si-NT FETs)

In this paper, an analytical model of the threshold voltage for short-channel symmetrical silicon nano-tube field-effect-transistors (Si-NT FETs) is presented. The three-dimensional (3D) Poisson equation in cylindrical coordinates has been solved with suitable boundary conditions to find the surface potential along the channel length. The inversion charge density \((Q_{inv} )\) has been calculated in the channel region of the device in the subthreshold regime of device operation, using the Boltzmann relationship. Subsequently, the calculated inversion charge density \((Q_{inv} )\) has been equated to a threshold charge density \((Q_{th})\) in order to find the threshold voltage \((V_{th})\) expression. The effect of physical device parameters, including the tube thickness, on the threshold voltage and drain induced barrier lowering (DIBL) of the device has been discussed. The model results have been verified with the simulation data obtained by the device simulation software ATLAS.     

Theory of abnormal thyristor forward voltage behavior

The on-state current-voltage characteristic of thyristors is investigated by numerical simulation. For sufficiently high p-base concentration-as already known-an abrupt increase in on-state voltage is observed above a critical current density. Driving the device to higher currents results in a reduction of on-state voltage. Similar results are obtained for thyristor profiles with very shallow emitters. An analytic model that explains the described phenomena from first principles and leads to a simple criterion for current limiting in terms of Gummel numbers and carrier mobilities is presented     

多脉冲均匀介质阻挡放电特性的仿真及实验研究

为了简化实验,优化反应器设计,扩大均匀介质阻挡放电的应用范围,基于用电压控制电流源(VCCS)模拟均匀放电过程的介质阻挡放电(DBD)等效电路模型,利用Simulink建立了大气压多脉冲均匀DBD的动态仿真模型。模型中采用适于表征均匀DBD的VCCS激励信号,建立了开关控制模块再来对VCCS进行控制,从而实现对放电电流脉冲个数的调节。利用所建模型对大气压氖气中平板电极结构DBD的电气特性进行了仿真,得到了不同条件下多脉冲均匀DBD的电压电流波形以及Lissajous图形。同时,建立了大气压氖气中DBD实验装置并对不同电压幅值下的放电特性进行了实验研究,还将仿真与实验所得到的结果进行了比较。结果表明,利用所建模型仿真得到的电压电流图形和Lissajous图均与实验测量结果相符合,验证了仿真模型的正确性。利用仿真模型进一步计算得到了实际实验过程中无法直接测量获得的放电参量,如气隙电压、介质电压、放电电流、放电功率、传输电荷等。由仿真得到的伏安特性曲线可知,氖气中多脉冲放电除第1次脉冲放电为Townsend放电转化为辉光放电,其余脉冲放电皆为辉光放电。     

Quantum drift-diffusion model for IMPATT devices

Quantum correction is necessary on the classical drift-diffusion (CLDD) model to predict the accurate behavior of high frequency performance of ATT devices at frequencies greater than 200 GHz when the active layer of the device shrinks in the range of 150–350 nm. In the present work, a quantum drift-diffusion model for impact avalanche transit time (IMPATT) devices has been developed by incorporating appropriate quantum mechanical corrections based on density-gradient theory which macroscopically takes into account important quantum mechanical effects such as quantum confinement, quantum tunneling, etc. into the CLDD model. Quantum potentials (synonymous as Bohm potentials) have been incorporated in the current density equations as necessary quantum mechanical corrections for the analysis of millimeter-wave (mm-wave) and Terahertz (THz) IMPATT devices. It is observed that the large-signal (L-S) performance of the device is degraded due to the incorporation of quantum corrections into the model when the frequency of operation increases above 200 GHz; while the effect of quantum corrections are negligible for the devices operating at lower mm-wave frequencies.     

Threshold voltage modeling for dual‐metal quadruple‐gate (DMQG) MOSFETs

In this paper, a three‐dimensional (3D) model of threshold voltage is presented for dual‐metal quadruple‐gate metal‐oxide‐semiconductor field effect transistors. The 3D channel potential is obtained by solving 3D Laplace's equation using an isomorphic polynomial function. Threshold voltage is defined as the gate voltage, at which the integrated charge (Q_inv) at the ‘virtual‐cathode’ reaches to a critical charge Q_th. The potential distribution and the threshold voltage are studied with varying the device parameters like gate metal work functions, channel cross‐section, oxide thickness, and gate length ratio. Further, the drain‐induced barrier lowering has also been analyzed for different gate length ratios. The model results are compared with the numerical simulation results obtained from 3D ATLAS device simulation results. Copyright © 2015 John Wiley & Sons, Ltd.     

An analytical model of triple‐material double‐gate metal–oxide–semiconductor field‐effect transistor to suppress short‐channel effects

This paper presents an analytical subthreshold model for surface potential and threshold voltage of a triple‐material double‐gate (DG) metal–oxide–semiconductor field‐effect transistor. The model is developed by using a rectangular Gaussian box in the channel depletion region with the required boundary conditions at the source and drain end. The model is used to study the effect of triple‐material gate structure on the electrical performance of the device in terms of changes in potential and electric field. The device immunity against short‐channel effects is evaluated by comparing the relative performance parameters such as drain‐induced barrier lowering, threshold voltage roll‐off, and subthreshold swing with its counterparts in the single‐material DG and double‐material DG metal–oxide–semiconductor field‐effect transistors. The developed surface potential model not only provides device physics insight but is also computationally efficient because of its simple compact form that can be utilized to study and characterize the gate‐engineered devices. Furthermore, the effects of quantum confinement are analyzed with the development of a quantum‐mechanical correction term for threshold voltage. The results obtained from the model are in close agreement with the data extracted from numerical Technology Computer Aided Design device simulation. Copyright © 2015 John Wiley & Sons, Ltd.     

Hybrid-model transient stability simulation using dynamic phasors based HVDC system model

A novel hybrid-model transient stability simulation algorithm for ac/dc power systems is suggested in this paper, where dynamic phasors theory is applied for HVDC transmission system modeling, and traditional electromechanical transient models are used for ac system. A detailed dynamic-phasors-based HVDC system model is derived first, and the algorithm for interface of the dc dynamic phasors model to ac network is proposed next. Computer simulation results show that the HVDC dynamic phasors model has very good accuracy as compared with its electromagnetic transient model; the test results from a 2-area ac/dc power system and a multi-infeed HVDC power system show clearly that the suggested interface algorithm works effectively in system transient stability analysis. The proposed hybrid-model simulation algorithm provides a new approach for dynamic simulation of large-scale ac/dc power systems.