Monte Carlo simulation of low-field mobility in strained double gate SOI transistors

Electron transport in strained double gate silicon on insulator transistors has been studied by Monte Carlo method. Poisson and Schroedinger equations have been self-consistently solved in these devices for different silicon layer thicknesses both for unstrained and strained silicon channels. The results show that the strain of the silicon layer leads to a larger population of the no-primed subbands, thus decreasing the average conduction effective mass. However, strain also contributes to a larger confinement of the charge close to the two Si/SiO₂ interfaces, thus weakening the volume inversion effect, and limiting the potential increase of the phonon limited mobility.     

NEGF simulations of the effect of strain on scaled double gate nanoMOSFETs

The effect of biaxial strain on double gate (DG) nanoscaled Si MOSFET with channel lengths in the nanometre range is investigated using Non-Equilibrium Green’s Functions (NEGF) simulations. We have employed fully 2D NEGF simulations in order to answer the question at which body thickness the effects of strain is masked by the confinement impact. Following ITRS, we start with a 14 nm gate length DG MOSFET having a body thickness of 9 nm scaling the transistors to gate lengths of 10, 6 and 4 nm and body thicknesses of 6.1, 2.6 and 1.3 nm. The simulated I _D–V _G characteristics show a 6% improvement in the on-current for the 14 nm gate length transistor mainly due to the energy separation of the Δ valleys. The strain effect separates the 2 fold from the 4 fold valleys thus keeping mostly operational transverse electron effective mass in the transport direction. However, in the device with an extreme body thickness of 1.3 nm, the strain effect has no more impact on the DG performance because the strong confinement itself produces a large energy separation of valleys.     

Two dimensional analytical modeling of a high-K gate stack triple-material double gate strained silicon-on-nothing MOSFET with a vertical Gaussian doping

This paper presents the two-dimensional analytical modeling of high-k gate stack Triple material double gatestrained SON MOSFET with a vertical Gaussian-like doping profile. The expression for surface potential has been calculated by solving the 2-D Poisson’s equation and by considering the parabolic potential approximation. The threshold voltages as well as the electric field are also calculated for the proposed model. In addition, detailed studies of the device response towards the various short-channel effects are also examined. The analytical results are verified using the results obtained from a 2-D device simulator, namely ATLAS, Silvaco.     

Use of the scattering matrix for device simulations

The use of the quantum mechanical scattering matrix is a time proven method for determining the transport probability for an electron wave in a nanostructure. When coupled with the Landauer formalism, it provides a valuable approach for simulation of semiconductor devices. Here, we discuss a numerically stable method to solve this transmission problem in a recursive manner. It is easily extended to dissipative and far from equilibrium situations. We also discuss the use of scattering matrices in photo excitation of nanostructures.     

Development of electronic device simulations for educational purposes

A comprehensive set of semiconductor device simulation tools, written in Java, is being developed for instructional use. These interactive programs can be launched from an electronic textbook or from lecture presentation material. At present these tools demonstrate introductory quantum mechanics, several aspects of semiconductor physics, and both zero-current and drift-diffusion device simulations in one dimension. Development of two-dimensional simulations is in progress.     

水轮机筒阀动水关闭过程的三维非定常数值模拟

在充分考虑筒阀与邻近部件之间相互影响的基础上,本文以水轮机全流道为研究对象,利用非结构化网格划分计算区域,采用RNG k-ε湍流双方程模型对筒阀内部非定常流动进行研究,并对筒阀及上下游相关的水轮机各过流部件在动水关闭状态下进行数值模拟,着重分析并得出了水轮机筒阀周边流场及引水部件蜗壳、固定导叶和活动导叶在筒阀不同开度下的压力和流速分布等流态特征,这些流态特征的分析可以预测混流式水轮机的工作状态,防止飞逸现象的发生,同时也为水轮机筒阀电液同步控制系统提供设计和操作参数等理论依据。     

Study of parallel numerical methods for semiconductor device simulation

Simulators of semiconductor devices have to solve systems of equations generated by the discretization of partial differential equations, which are the most time‐consuming part of the simulation process. Therefore, the use of an effective method to solve these linear systems is essential. In this work we have evaluated the efficiency of different parallel direct and iterative solvers used for the solution of the drift–diffusion equations in semiconductor device simulation. Several preconditioning techniques have been applied in order to minimize the execution times. We have found that FGMRES and BCGSTAB solvers preconditioned with Additive Schwarz are the most suitable for these types of problems. The results were obtained in an HP Superdome cluster with 128 Itanium2 1.5 GHz. Copyright © 2005 John Wiley & Sons, Ltd.     

大跨度闸门双液压缸启闭机的同步控制方法

为解决大型闸门双液压缸启闭机偏差不易控制的问题,以丰满大坝溢流闸门液压启闭机为例,阐述了一种以速度粗调和位置精调相结合的双液压缸启闭机同步控制方法.实际运行结果表明,该控制方法同步精度较高、工作较为可靠,符合运行要求.     

斜板对竖流式沉淀池影响的三维数值模拟

在考虑加入斜板的条件下,对竖流式沉淀池进行数值模拟,分析斜板对竖流式沉淀池工作效率的影响,对沉淀池的结构优化及改善沉淀池的工作效率提供理论依据。选取Mixture模型和RNG k-ε模型,构建有无斜板两种竖流式沉淀池并对其进行三维数值模拟,得到了沉淀池内部流态和悬浮物浓度分布等情况。在竖流式沉淀池内部由于漩涡的产生,湍动能增大,并带动污泥向上发展,加入斜板对竖流式沉淀池的结构进行优化后,斜板阻止了漩涡向上发展的趋势,对沉淀池的效率有较大影响。斜板竖流式沉淀池能有效避免入流初期异重流的发生,改善了竖流式沉淀池的内部流态;加入斜板后使沉淀面积增大,斜板阻挡了悬浮物向上流动,有效的提高了出口处水质;同时证明了对沉淀池进行合理的结构改变能改善沉淀池的工作效率。     

An efficient numerical technique for the implementation of SSLS and cyclostationary noise analysis in physics-based device simulators

The paper introduces a novel numerical technique for the efficient implementation of SSLS and cyclostationary noise analysis in physics-based device simulators calculating the time-varying device working point exploiting the harmonic balance technique. The technique is based on a mixed time-frequency evaluation of the matrix-vector products involved in the iterative solution of linear systems, indispensable for the simulation of realistic 2D or 3D device structures, relevant to the previous analyses. The algorithm, applicable to all PDE systems where the memory part is linear, allows for a significant improvement in the computation time with respect to the direct, frequency-domain implementation.     

基于双DSP结构的中低压线路保护测控装置的设计

设计了一种适用于中低压线路的保护测控装置,它采用双DSP结构,充分利用了数字信号处理器的速度快、精度高的优点,保护与测控功能独立实现,既保证保护的可靠性,也保证了测量的高精度。文中介绍了保护测控装置的硬件组成和软件模块的实现。     

水工弧形闸门流激振动特性物模-数模联合预测与安全分析

水利工程中的弧形闸门对整个枢纽的安全至关重要,而水流诱发闸门振动现象很普遍,其动力安全关系到整个枢纽建筑物的安全,对闸门流激振动响应的合理预测是水利工程中的一项重要研究课题。基于嘉陵江新政工程弧形闸门实例,运用物理模型和数学模型对该闸门流激振动特性进行了预测,综合考虑了整个闸门体系的耦合作用以及流固耦合效应,用物理模型仿真模拟了水力系统-闸门结构系统-支撑系统（闸墩）整体耦联振动,强调闸墩对闸门振动的影响,突破了以往将闸墩处理成刚性的方法。提出用三维板壳单元建立闸门空间数学模型并进行动力分析,最后联合物理模型和数学模型对其进行了动力安全分析,提出避免危害振动的措施。     

110 kV双回路转角塔等电位作业进电场装置的研制与应用

在110 kV双回路转角塔等电位作业时,传统等电位作业进电场的方式无法满足等电位作业安全距离,因此,分析研究110 kV双回路转角塔的结构特点,并参考“塔吊”的工作原理,研制了一种等电位作业进电场装置,改变传统带电作业进电场的方式和路径,增大组合间隙,保证了作业人员在110 kV双回路转角塔开展等电位作业时进入强电场的安全距离,具有很强的实用性,保证供电可靠性。     

Accelerated convergence in numerical simulations of surface supersaturation for crystal growth in solution under steady‐state conditions

This is an investigative paper which reports the results of comparisons of two numerical techniques for the solution of the Burton Cabrera and Frank (BCF) equation for the growth on crystal surfaces under steady state conditions. A successive over‐relaxation (SOR) scheme for the equivalent finite difference equation gives rapid convergence to the static solution. It is known that a suitable choice of scattering parameters in a transmission line matrix (TLM) network analogue of the Laplace equation yields ultra‐fast convergence. The results of numerical experiments which are reported here suggests that a similar situation also applies to the solution of the Poisson equation with shunt losses (the BCF equation), although the choice of optimum conditions appears to be different for different spatial positions within the solution space. Copyright © 2005 John Wiley & Sons, Ltd.     

Investigation of a novel SOI LDMOS using p+ buried islands in the drift region by numerical simulations

A novel SOI LDMOS with p+ buried islands and p-top layer in the drift region (PBI SOI) is proposed in this letter. At off-state, the high potential is induced from the drain region to the inside of the drift region. The p+ buried islands cause reduced surface field effect and modulate the electric field distribution in the drift region. The buried p-top layer withstands the lateral drain voltage. Thus, the breakdown voltage (BV) of PBI SOI is significantly improved. Meanwhile, the specific on-resistance \((R_\mathrm{on,sp})\) is reduced by improving doping concentration of the drift region, owing to the assisting depletion effect caused by the p+ buried islands. Consequently, the \(R_\mathrm{on,sp}\) of the proposed structure is reduced by 53.7% compared with the conventional SOI LDMOS at the same half-pitch size, the BV and the figure-of-merit \((\hbox {FOM} = \hbox {BV}^{2}/ R_\mathrm{on,sp})\) are observably improved by 24.8% and 235.9% respectively.     

On the robustness of numerical algorithms for linear systems and signal processing in finite precision arithmetic

This paper proposes a model of the perturbations resulting from finite precision arithmetic implementation of numerical methods. Iterative methods for linear systems are represented as control systems, and the numerical errors caused by finite precision are represented as a multiplicative uncertainty. This representation makes it possible to use results from robust control theory to provide stability criteria, which, in turn, imply convergence, under finite precision arithmetic, of algorithms considered. Numerical examples are taken from several fields in order to illustrate the theoretical results. Copyright © 2015 John Wiley & Sons, Ltd.