A parallel 3D semiconductor device simulator for gradual heterojunction bipolar transistors

In this paper, we present a parallel three‐dimensional semiconductor device simulator for gradual heterojunction bipolar transistor. This simulator uses the drift‐diffusion transport model. The Poisson equation and continuity equations were discretized using a finite element method (FEM) on an unstructured tetrahedral mesh. Fermi–Dirac statistics is considered in our model and a compact formulation is used that makes it easy to take into account other effects such as the non‐parabolic nature of the bands or the presence of various subbands in the conduction process. Domain decomposition methods were tested to solve the linear systems. We have applied this simulator to a gradual heterojunction bipolar transistor (HBT), and we present some measures of the parallel execution time for several solvers and some electrical results. This code has been implemented for distributed memory multicomputers, making use of the MPI message passing standard library and a parallel solver library. Copyright © 2002 John Wiley & Sons, Ltd.     

An improved model to predict DC characteristics of organic field-effect transistors

Journal of Computational Electronics - Organic field-effect transistors (OFETs) are becoming popular because of the ease associated with their fabrication and cost-effectiveness. Numerous models...     

Modeling of graphene-based field-effect transistors through a 1-D real-space approach

In this work, we present a computationally efficient approach for atomistic simulations of graphene nanoribbon (GNR), bilayer graphene (BLG) and bilayer graphene nanoribbon (BLGNR) field-effect transistors. The simulation scheme, which involves the self-consistent solutions of the non-equilibrium Green function method (NEGF) and 2-D Poisson’s equation, is based on the tight binding Hamiltonian in a 1-D real-space basis. We show that the Hamiltonian matrix for smooth edge GNRs and graphene can be expressed by 1 \(\times \) 1 size coupling matrices, which provides easy solutions for NEGF equations and largely reduces the computational time for simulation. The BLG and BLGNR can be described by the two coupled single-layer GNR Hamiltonian matrices, which allows the modeling of these devices by the same transport equations as GNR-FET with small modifications. Furthermore, the developed transport models are verified with the previously reported simulation and theoretical results.     

Nonlinearity and scaling trends of quasiballistic graphene field-effect transistors targeting RF applications

Journal of Computational Electronics - Graphene field-effect transistors (GFETs) based on ballistic transport represent an emerging nanoelectronics device technology with promise to add a new...     

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.     

基于Terra Vista的流域地形三维建模方法

三维地形建模是实现流域仿真模拟的基础工作,快速智能地生成三维地形则是地形建模的关键技术。本文结合都江堰流域地形模拟,基于Terra Vista软件进行了建模方法研究。将地形等高线资料、遥感影像资料和道路、水系、渠道、建筑物、植被等经过转换配准后,以地形DEM、遥感影像、矢量数据的形式集成于一体载入Terra Vista,统一生成了都江堰地形模型。文章阐述了地形生成的具体步骤,探讨了流域摸拟中天然河道和人工渠道的建模技术,为流域模拟仿真提供了快速智能的三维地形生成方案。     

煤场盘点三维模型的建立

煤场存煤量的盘点是电厂燃料管理的重要组成部分,目前常用的盘点工具是激光电脑盘煤仪,它采用三角剖分算法,对采集到的煤堆表面的三维数据点集进行拟合,使拟合出的曲面能够更好地逼近煤堆表面,采用光照和消隐处理后,使绘出的图形更逼真。针对激光电脑盘煤仪在湛江电厂实际应用中使用的误差问题,对激光电脑盘煤仪的软件部分进行了改进,优化了算法,一是除去封闭点,二是编写了独立的边生长算法作为独立的子程序,改进后的激光电脑盘煤仪在实测中效果良好。     

Characterization of Au/Pb(Zr0.96Ti0.04)O3/Al2O3/Si antiferroelectric field-effect transistors for memory application

Polarization-voltage (P-V) hysteresis loops and polarization retention were studied for Au/Pb(Zr_0.96Ti_0.04)O₃/Al₂O₃/Pt antiferroelectric capacitors with different Al₂O₃ layer thicknesses. The high-field ferroelectric phase after poling can be pertained to zero external field with the choice of an appropriate Al₂O₃ layer thickness. At the same time, a strong depolarization field across the Al₂O₃ layer is generated with the direction opposite to the field across the Pb(Zr_0.96Ti_0.04)O₃ layer. The depolarization-field direction can be reversed with the domain switching of the high-field ferroelectric phase, possessing the potential application of antiferroelectric memories. A large memory window of 10 V was observed for Au/Pb(Zr_0.96Ti_0.04)O₃ (50 nm)/Al₂O₃ (6.3 nm)/n-Si (100) field-effect transistors, as confirmed from the capacitance sweeping under voltages between ?19 and +19 V. The high/low capacitance ratio is over 8:1, and the ratio remains stable with time over 4 h after programming voltage of ±19 V at 80°C, in suggestion of the excellent retention of the memory.     

3D numerical modeling of Quantum Dot using homotopy analysis

The 3D numerical modeling of nanoscale InGaAs quantum dot is developed and the characteristics of the device are presented. The exact potential and energy profile of the Quantum Dot are computed by obtaining the solution of 3D Poisson and Schrodinger equations using homotopy analysis. The dark current is estimated by considering the Quantum Dot density, applied voltage, length of quantum dot array, number of quantum dot array and temperature. The results obtained show that the dark current is strongly influenced by Quantum Dot density and applied voltage. The developed model is physics based one and overcomes the limitations of the existing analytical models. The model is validated by comparing the results obtained with the existing models.     

基于VPB和osgGIS的流域三维虚拟环境建模方法

三维虚拟环境建模是实现流域虚拟仿真模拟的基础工作,快速智能地生成三维地形地物则是流域建模的关键技术。结合松花江流域地形建模和哈尔滨市建筑物建模,基于VirtualPlanetBuilder（VPB）和osgGIS进行了地形地物建模方法研究。阐述了基于地形DEM和遥感影像的流域多层次地形建模技术,探讨了多源数据的组织与利用方法。分别研究了线状地物和面状地物的参数设置方法,包括线状地物随地形起伏的设置、建筑物高度及顶面与侧面纹理的设置等。基于VPB和osgGIS的建模方法可以支持不同格式、不同精度和坐标系的原始数据,建模自动化程度高,生成的模型支持多层细节和基于外存的调度模式,可以为海量模型的实时调度渲染提供模型支持,是流域仿真模拟中三维地形地物的快速生成方案。     

基于Terra Vista的调水工程大规模三维地形建模技术

三维地形建模是实现大型水利工程虚拟仿真的基础工作,快速智能地生成三维地形并满足实时仿真对模型精度及渲染速度的要求则是大规模地形建模的关键.本文结合引渤济锡调水工程地形模拟,进行了基于Terra Vista软件的建模方法研究.阐述了地形生成的具体步骤,探讨了大地形的变比例建模、地形数据库参数设置、地形分块与精度匹配、自建模型的智能嵌入等技术,为大型水利工程虚拟仿真提供了快速智能的三维地形生成方案.     

Improved analytical modeling of conductive losses in gappedhigh-frequency inductors

An improved method to predict conductive losses in gapped high-frequency inductors is presented and used for parametrization of an equivalent small-signal circuit model. The method is based on the superposition of power losses resulting from the well-known one-dimensional (1-D) field calculation and losses due to eddy currents caused by the fringing field of air gaps determined from novel analytical two-dimensional field calculations. Losses due to reactive currents in the windings caused by self capacitances are also considered. A greatly improved accuracy compared to 1-D analysis is proved by measurements     

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.     

Analysis and modeling of the transient local tunneling in gate oxides

This work presents a detailed investigation of the local transient tunneling currents due to substrate- and gate-near traps generated by Fowler-Nordheim stress in nitrided oxide MOS structures. We demonstrate that for the correct interpretation of the transient stress-induced leakage currents measured in the external circuit, it is essential to include the effects of the substrate and poly-Si capacitances. This leads to gate-voltage-dependent weighting factors, which relate the measured current transients to the local trap tunnel currents near the substrate and the gate. By a combination of these measurements with transient capacitance measurements, it is possible to separately determine the local tunnel currents and, thus, the densities of traps generated close to the substrate and to the gate.     

Efficient full-flow process simulation for 3D structures including stress modeling

The need to use 3D process simulation increases as device dimensions shrink and new 3D device designs emerge. Moreover, many state-of-the art CMOS devices employ some sort of stress engineering, which necessitates 3D stress simulations. To perform these simulations efficiently and quickly, new methodologies need to be employed. In this paper we demonstrate several applications of the next generation TCAD tools to 3D simulation problems critical for understanding and development of modern devices.     

基于TOF相机的喷涂工件在线三维重建

喷涂生产线轨迹规划和喷涂机器人自编程技术大都以工件的在线三维测量为基础。近年来TOF相机作为一种高性价比的3D成像设备,被应用于工件测量。针对TOF相机成像视场有限、单次成像只能获取局部轮廓深度信息等问题,提出一种基于工件在位旋转和图形处理器(GPU)加速的TOF点云视频流三维重建算法。该方法在有向距离函数(SDF)点云融合基础上,采用空间散列表存储管理海量点云数据,同时引入快速视觉里程(FOVIS)算法用于姿态估计,以提高喷涂工件在位三维重建算法的效率和鲁棒性。喷涂生产线仿真平台实验表明,在线重建过程中平均帧数可达58 f/s,失败率≤2%,显存占用率25%,为随后的三维测量和喷涂轨迹规划提供完整的点云数据。     

一种基于混合采样的雷达作用范围三维建模方法

针对雷达作用范围二维表现方式的不足,提出了一种基于混合采样的雷达作用范围三维建模方法。以雷达方程为基础,通过地形分辨率网格确定雷达方位角方向的采样步长,使雷达模型对不同精度地形具有自适应性。以雷达的3dB特征点为基准,对雷达俯仰角进行分区域采样,在保证模型外形与雷达特征属性一致的同时有效减少了绘制点的数目。实验结果表明,基于混合采样的三维建模方法不仅能快速、准确完成雷达三维建模,而且能更加直观地展现雷达探测范围。     

基于三维实景模型的水库无线视频监控系统

以前坪水库为例，水库建设期视频监控系统信号采用无线网桥传输，基于无人机航摄生成三维实景模型进行视频监控点及无线网桥布置设计。介绍了采用大疆无人机DJ1 PHANTOM4 PRO进行航飞倾斜摄影，采用Context Capture 3D生成三维实景模型的过程步骤，对基于三维实景模型优化监控点布设及视野和信道复核的方法进行了研究。实践表明，基于无人机三维实景模型的水库无线视频监控系统设计可靠，可为其他类似工程参考借鉴。