Atomistic Simulation of Carbon Nanotube Field-Effect Transistors Using Non-Equilibrium Green’s Function Formalism

Carbon Nanotube (CNT) Electronics attracts much attention for both basic and applied research. We first review a previously developed atomistic simulator for ballistic carbon nanotube transistors [1]. A recent work shows that our modeling of electrostatics, quantum transport, and contacts is sufficient to describe experiment [2]. A self-consistent atomistic simulation for a CNTFET imposes significant computational challenges. In this paper, we show how to efficiently implement the atomistic simulation by using computational techniques for computing Green’s function, solving 3D Poisson equation, running parallel simulation, and improving convergence. A phenomenological model of metal/CNT contacts suitable for routine device simulation is also discussed in detail.     

Advanced Simulation of Semiconductor Devices by Artificial Neural Networks

Characterization and modelling of transistors for advanced microwave electronics is very useful to understand and improve device performances. Here, a modelling procedure of HEMT transistors for microwave applications is described. There are many different approaches to this problem, such as direct extraction methods, global or decomposed fitting techniques and inverse modeling issues. In this paper, we use an Artificial Neural Network (ANN) to extract a 17-element small signal circuit model. By this procedure we are able to identify the model from one measured [S] parameters set. Several circuit model values have been extracted by varying the temperature and the bias operating conditions. To our knowledge, these are the first results of a complete equivalent circuit extracted by an ANN technique without the need for any final tuning of the variables.     

大气散射方向指数函数研究

在天空亮度分布中,大气散射方向指数占有非常重要的地位,以往的研究忽略了大气混浊度因子对散射方向指数的影响。本文在散射方向指数中考虑大气混浊度因子的影响,提出了新的大气散射方向指数函数,对不同混浊度因子,此函数与已知的晴天、部分云天和似阴天空有较好的近似,并更全面地考虑了分子散射,对进一步研究中间天空亮度分布具有理论意义。     

Monte Carlo Simulation of Electronic Noise in Semiconductor Materials and Devices Operating under Cyclostationary Conditions

To qualify the feasibility of standard semiconductor materials and Schottky-barrier diodes (SBDs) for THz high-order harmonics generation and extraction, the noise-to-signal ratio is calculated by the Monte Carlo method. Heavily doped GaAs SBDs are found to exhibit conditions for frequency mixing and harmonics extraction which are definitively superior to those of bulk materials.     

Coherent Phonon Scattering in Molecular Devices

In the present work we investigate the influence of molecular vibrations on the tunneling of electrons through a molecule sandwiched between two metal contacts. The study is confined to the elastic scattering only, but beyond the harmonic approximation. The problem is tackled both from a classical and a quantum-mechanical point of view. The classical approach consists in the computation of the time-dependent current fluctuations calculated at each step of a molecular dynamics (MD) simulation. On the other hand, the vibrational modes are treated quantum-mechanically and the tunneling current is computed as an ensemble average over the distribution of the atomic configurations obtained by a suitable approximation of the density matrix for the normal mode oscillators. We show that the lattice fluctuations modify the electron transmission. At low temperatures the quantum-mechanical treatment is necessary in order to correctly include the zero-point fluctuations. However, for temperatures higher than few hundreds Kelvin the simple harmonic approximation which leads to the phonon modes breaks because the oscillation amplitudes of the lowest energy modes become large.     

保护大容量半导体装置的熔断器

介绍了一种保护半导体装置用的薄膜型熔断器的特点、结构和有关制造技术。它具有良好的限充作用、较低的允通焦耳积分和熔体电流密度（６ｋＡ／ｍｍ＾２以上），熔断器外形尺寸小和特性稳定，是一种今后保护半导体装置用的熔断器的发展方向。     

A Non-Parabolic Six Moments Model for the Simulation of Sub-100 nm Semiconductor Devices

Macroscopic transport models derived from Boltzmann’s equation by using the method of moments are often used to efficiently evaluate the electrical behavior of semiconductor devices. The most commonly used model is the drift-diffusion model which comprises the first two moments of Boltzmann’s equation. In this model the carrier gas is assumed to be in equilibrium with the lattice, an assumption severely violated in submicron semiconductor devices. Hydrodynamic and energy-transport models have therefore been proposed to overcome this limitation. However, these extended models have never been widely accepted as a viable substitute, because for small devices they often do not deliver the expected improved accuracy. Here we present a non-parabolic six moments model which predicts considerably more accurate currents than the energy-transport model down to gate-lengths as small as 40 nm.     

高压半导体功率器件的寿命控制工程述评

对应用于高压功率器件的寿命控制技术进行了述评。着重分析了高能H^ 辐照、He^2 辐照等局域寿命控制技术，利用这种技术有可能实现高压功率器件突破性的进展。     

Quantum Corrected Monte Carlo Simulation of Semiconductor Devices Using the Effective Conduction-Band Edge Method

In recent years much effort has been devoted to the quantum mechanically corrected Monte Carlo simulation of nano-scale semiconductor devices. The effective potential and the Wigner or the Bohm quantum potential are usually chosen for making such quantum correction. In this study we propose another approach based on the Bohm potential by transforming the density gradient to an effective conduction-band edge gradient. Similar to the effective potential method, this method has the advantage of not being affected by density fluctuations. We have applied this method to the simulation of a double-gate nMOSFET. Results are compared to those obtained from the semi-classical Monte Carlo simulation without the quantum correction.     

用ANSYS软件包模拟半导体器件散热器稳态热阻

介绍了ANSYS多物理场软件包的流动传热仿真分析特点、功率半导体器件用的散热器稳态热阻的理论分析及计算仿真的基本过程。所得出的一系列仿真结果与实验数据是吻合的，证明了仿真理论的正确性。     

A Non Perturbative Model of Surface Roughness Scattering for Monte Carlo Simulation of Relaxed Silicon n-MOSFETs

In the present paper the problem of interface roughness scattering is treated non-perturbatively by incorporating the effects of scattering as a boundary condition for the Boltzmann transport equation (BTE). This provides a basis for the development of a semi-classical model of the interface roughness scattering mechanism applicable to the Monte Carlo (MC) simulations of electron transport in the Si n-MOSFET. The model is based on the Boltzmann-Fuchs method for the solution of the BTE. This method has shown to be computationally efficient and is naturally suited to the semi-classical spirit of the BTE and its direct solution via the MC method.     

Random Doping Fluctuations of Small-Signal Parameters in Nanoscale Semiconductor Devices

Random dopant induced fluctuations of small-signal parameters in nanoscale semiconductor devices are analyzed by using the perturbation (linearization) technique. This technique requires only first-order derivatives of the transport equations, which makes it suitable for implementation in commercial device simulators. Sample numerical results are presented for a 25 nm channel length n-channel MOSFET device.     

采用计算机高速数值采集系统实现电力电子器件的参数测试

通过将计算机，高速数据采集卡和相应的辅助电路与软件组成计算机高速数据采集系统，可以实现电力电子器件的参数测试，本文对相关的内容作了详细的分析。     

Improved Configuration of Multilevel Inverter with Reduced Semiconductor Devices

In DC/AC power conversion, multi-level inverter (MLI) incorporates a large number of semiconductor devices, which increases its cost and complexity. Moreover, the recently introduced topology uses a large variety of semiconductor switches. Therefore, a great attention is paid toward increasing output voltage levels with less variety and reduced number of switches as compared to conventional topologies. In this paper, improved configuration of symmetrical and asymmetrical MLI is proposed. Improvement is brought on both quantitative and qualitative basis, which led to a reduction in number of semiconductor devices and its variety. Analysis of power losses of the proposed topology is carried out and compared with CHB. A wide range of comparison with recently proposed topologies is made in order to show the novelty and contribution of the proposed topology. Multi-Carrier Pulse Width Modulation strategy is adopted for generating the switching pulses. The detailed simulation study of the proposed topology has been carried out using MATLAB/SIMULINK and validated experimentally for 7-level and 81-level inverter.     

碳化硅电力半导体器件在现代电力系统中的应用前景

随着智能电网的建设及可再生能源发电技术的发展,以碳化硅为代表的宽禁带半导体器件以其高功率密度、高电压、高频率、高热导率等优越的物理和电气特性,将在现代电力系统中扮演越来越重要的角色。本文主要介绍了碳化硅功率器件的最新进展,然后对碳化硅功率器件在现代电力系统中的应用前景(可再生能源发电、柔性直流输电、电能路由器、固态断路器)进行了分析和展望。     

电力电子器件及其应用的现状和发展

电力电子是现代科学、工业和国防的重要支撑技术,功率器件是电力电子技术的核心和基础,其应用是电力电子技术发展的驱动力。该文对现代电力电子器件,特别是碳化硅(SiC)和氮化镓(GaN)功率器件及当前电力电子应用装置/系统的诸多热点问题(绿色能源应用、电动汽车、LED照明)的现状和发展前景进行简要的综述。     

New Power Semiconductor Devices for Future Generations of Power Supplies

Power Semiconductors are still the driving force for many power electronic systems.In this paper the development of the key power semiconductors devices for power supplies are shown,and their electrical performance discussed.Future directions of the major power semiconductor devices like the IGBT,Super Junction technology and SiC device will be explained.     

The Use of Quantum Potentials for Confinement and Tunnelling in Semiconductor Devices

As MOSFETs are scaled to sub 100 nm dimensions, quantum mechanical confinement in the direction normal to the silicon dioxide interface and tunnelling (through the gate oxide, band-to-band and from source-to-drain) start to strongly affect their characteristics. Recently it has been demonstrated that first order quantum corrections can be successfully introduced in self-consistent drift diffusion-type models using Quantum Potentials. In this paper we describe the introduction of such quantum corrections within a full 3D drift diffusion simulation framework. We compare the two most popular quantum potential techniques: density gradient and the effective potential approaches, in terms of their justification, accuracy and computational efficiency. The usefulness of their 3D implementation is demonstrated with examples of statistical simulations of intrinsic fluctuation effects in decanano MOSFETs introduced by discrete random dopants. We also discuss the capability of the density gradient formalism to handle direct source-to-drain tunnelling in sub 10 nm double-gate MOSFETS, illustrated in comparison with Non-Equilibrium Green's Functions simulations.     

A Direct Solver for 2D Non-Stationary Boltzmann-Poisson Systems for Semiconductor Devices: A MESFET Simulation by WENO-Boltzmann Schemes

We present preliminary results of a high order WENO scheme applied to deterministic computations for two dimensional formulation of the transients for the Boltzmann-Poisson system describing electron transport in semiconductor devices. The collisional term models optical-phonon interactions which become dominant under strong energetic conditions corresponding to nanoscale active regions under applied bias. We treat the Boltzmann Transport equation in a spherical coordinate system for the wave-vector space. The problem is three dimensional in the wave-vector space and two dimensional in the physical space, plus the time variable driving to steady states. The new formulation avoids the singularity due to the spherical coordinate system.