Monte Carlo simulation of bipolar transistors

A new approach is proposed to investigate, the limits of validity of the conventional drift-diffusion equation analysis for modeling bipolar transistor structures containing submicrometer dimensions. The single-particle Monte Carlo method is used for the solution of the Boltzmann equation. An electron velocity overshoot of 1.8 times the static saturation velocity has been found for electrons near the base-collector junction of a silicon device. The effect of this velocity overshoot was calculated to enhance the output collector current and reduce the electron transit time by 5 percent for the device structure considered in this work.     

皮肤三层模型的Monte Carlo法模拟激光多普勒血流测量

本文提出了用Monte Carlo法模拟光子流在表皮、真皮及皮下组织中的传播。经过对模拟结果的分析,提出通过改变环状探测器与入射光束的距离来探测不同深度血流层的血流速度;发现频谱的指数下降规律;指出在血球浓度较小时,平均频移反映红血球的平均速率,在浓度较高时反映红血球的均方根速率;本文还给出了不同血球浓度下光子的穿透深度。     

Monte Carlo simulation and random number generation

Methods of generating pseudorandom number sequences that might have predetermined spectral and probability distribution functions are discussed. Such sequences are of potential value in Monte Carlo simulation of communication, radar, and allied systems. The methods described are particularly suited to implementation on microcomputers, are machine portable, and have been subjected to exhaustive investigation by means of both statistical and theoretical tests     

Monte Carlo simulation of growth of nanowhiskers

The growth of silicon nanowhiskers on the Si (111) surface activated with Au is studied by Monte Carlo simulation. The dependences of the rate of growth of whiskers on the temperature, deposition rate, and catalyst droplet diameter are obtained, and the morphological properties of the growing wirelike nanocrystal are studied. In addition to the growth of nanowhiskers, a number of experimentally observed effects, such as migration of the droplet from the whisker top, faceting of the whisker sidewalls, and branching are established for the model system. It is shown that, under certain conditions of wetting of the whisker material with the catalyst, formation of hollow nanowhiskers is possible.     

Direct Monte Carlo simulation of hot-carrier conductivity

We present a Monte Carlo procedure which, by including the mechanism of generation and recombination from impurity centers, enables us to calculate directly from the simulation the field dependent conductivity for the first time. The reliability of the theoretical model has been checked by comparing numerical results with experiments provided by the Montpellier group and performed on p-Si at different acceptor concentrations and temperatures.     

Monte Carlo calculation and measurement of shot-noise reduction factor

The frequency characteristic of the shot-noise reduction factor (R²) of the "O"-type diode is investigated by three methods: the first is a Monte Carlo calculation following the approach of Tien and Moshman and changing the pseudorandom numbers; the second is a computer simulation of the reduction of the modulated electrons at the potential minimum; and the third is the experimental measurement of shot-noise reduction using photoemission electrons produced by a mode-locked ruby laser. It is found by the Monte Carlo calculation that the original results of Tien and Moshman are not characteristic of the general situation, especially with regard to the peak at the plasma frequency of the potential minimum, and with regard to the dip commonly called the Tien dip. Calculations of the shot-noise reduction factor both by the Monte Carlo method and by the computer simulation approach show a rather smooth high-pass frequency characteristic. This result is verified by the photoemission experiments where the measurement accuracy has been enhanced through the use of mode locking.     

Monte Carlo simulation of noncubic symmetry semiconductingmaterials and devices

In this paper, we discuss the complexities that arise in Monte Carlo based modeling of noncubic symmetry semiconductors and their related devices. We have identified three general issues, band structure, scattering mechanisms, and band intersections that require some modification of the Monte Carlo simulator from that for cubic symmetry. Owing to the increased size and number of atoms per unit cell, the band structure is far more complex in noncubic than in zincblende phase semiconductors. This added complexity is reflected by the greater number of bands, smaller Brillouin zone and concomitant increase in the number of band intersections. We present strategies for modeling the effects of band intersections on the carrier dynamics using the Monte Carlo method. It is found that the band intersection points greatly affect the carrier transport, most dramatically in the determination of the impact ionization and breakdown properties of devices and bulk material. Excellent agreement with experimental measurements of the impact ionization coefficients is obtained only when treatment of the band intersections is included within the model     

火灾探测器可靠性的Monte Carlo仿真

从“人-机-环境”的角度对导致火灾探测器误报、漏报的原因进行了分析，利用Monte Cario系统仿真方法对火灾探测器的可靠性进行了模拟分析，得到的探测器可靠度、故障率曲线与理论和工程实际情况相符。正确地描述了火灾探测器的故障率随时间变化的规律，为进一步应用该方法来分析整个火灾探测报警系统的可靠性提供了理论基础。     

Monte Carlo simulation of GaAs Schottky barrier behaviour

The transport of carriers through the space-charge region (SCR) of a GaAs Schottky barrier is studied by the Monte Carlo simulation technique. Simulation results indicate that the carrier distribution is significantly perturbed from a Max-wellian near the metal-semiconductor boundary, limiting the validity of the commonly used thermionic diffusion model. Phenomena related to the disturbed distribution include increased recombination velocity at the interface and reduced carrier concentration near the junction. The interface recombination velocity is found to be constant with applied bias and the Bethe condition is shown to be more than sufficient to ensure the validity of the thermionic emission model.     

Monte Carlo simulation of boron implantation into single-crystalsilicon

An improved Monte Carlo simulation model has been developed for boron implantation into single-crystal silicon. This model is based on the Marlowe Monte Carlo code and contains significant improvements for the modeling of ion implantation, including a newly developed local electron concentration-dependent electronic stopping model and a newly developed cumulative damage model. These improvements allow the model to reliably predict boron implant profiles not only as a function of energy, but also as a function of other important implant parameters such as tilt angle, rotation angle, and dose. In addition, profiles of implant generated point defects (silicon interstitials and vacancies) can be calculated     

FPGA-based Monte Carlo simulation for fault tree analysis

The reliability analysis of critical systems is often performed using fault-tree analysis. Fault trees are analyzed using analytic approaches or Monte Carlo simulation. The usage of the analytic approaches is limited in few models and certain kinds of distributions. In contrast to the analytic approaches, Monte Carlo simulation can be broadly used. However, Monte Carlo simulation is time-consuming because of the intensive computations. This is because an extremely large number of simulated samples may be needed to estimate the reliability parameters at a high level of confidence.In this paper, a tree model, called Time-to-Failure tree, has been presented, which can be used to accelerate the Monte Carlo simulation of fault trees. The time-to-failure tree of a system shows the relationship between the time to failure of the system and the times to failures of its components. Static and dynamic fault trees can be easily transformed into time-to-failure trees. Each time-to-failure tree can be implemented as a pipelined digital circuit, which can be synthesized to a field programmable gate array (FPGA). In this way, Monte Carlo simulation can be significantly accelerated. The performance analysis of the method shows that the speed-up grows with the size of the fault trees. Experimental results for some benchmark fault trees show that this method can be about 471 times faster than software-based Monte Carlo simulation.     

Bootstrap, an alternative to Monte Carlo simulation

The Monte Carlo simulation is a commonly used technique for circuit analysis, but is computationally expensive. The bootstrap method can save simulation time and retain the desired accuracy     

A Monte Carlo simulation algorithm for finding MTBF

Prediction of mean time between failures (MTBF) is an important aspect of the initial stage of system development. It is often difficult to predict system MTBF during a given time since the component failure processes are extremely complex. The authors present a Monte Carlo simulation algorithm to calculate the MTBF during a given time of a binary coherent system. The algorithm requires the lifetime distributions of the components and the minimal path sets of the system. The MTBF for a specific time interval, e.g. a month or a year, can be estimated. If the component lifetime distributions are unknown, then a lower bound of system MTBF can be estimated by using known constant failure rates for each component     

Improved sequential stopping rule for Monte Carlo simulation

This letter presents an improved result on the negative-binomial Monte Carlo technique analyzed in a previous paper1 for the estimation of an unknown probability p. Specifically, the confidence level associated to a relative interval [p/?2, p?1], with ?1, ?2 > 1, is proved to exceed its asymptotic value for a broader range of intervals than that given in the referred paper, and for any value of p. This extends the applicability of the estimator, relaxing the conditions that guarantee a given confidence level.     

Monte Carlo surface scattering simulation in MOSFET structures

The Monte Carlo method has been applied to MOSFET devices with the gate lengths less than 1 µm. The electric field in the channel was obtained by an analytical approach. Since the classical situation is approached in the submicrometer gate device, the partial diffusive model is employed for surface scattering process. Transient phenomena such as velocity overshoot have been predicted with drain biases causing a large field gradient in the channel. Comparison of the results of the Monte Carlo simulation with those obtained by an analytical approach based on static mobility shows that the carrier transit time in the channel is shorter (as much as two times) than that predicted by the analytical approach for a 0.3 µm gate device.     

基于云计算的蒙特卡罗模拟分析

为了提高蒙特卡罗模拟分析的效率,设计了一种以Platform Symphony为基础的云计算平台,并对平台进行了扩展和集成,详细论述了实现的过程以及关键技术。通过实验表明,该平台能够进行高性能计算,输出的结果精确,是实现蒙特卡罗模拟分析的实用工具。     

激光多普勒测量皮肤血流的Monte Carlo模拟

本文根据皮肤的双层模型,分别用两种相位函数给出光子与红血球碰撞的散射角,利用Monte carlo方法得出探测到的光子强度分布、光子数按频移的分布,以及总频移和平均频移与红血球浓度的关系。发现在低浓度时总频移与浓度呈线性,指出频移的强度涨落的一阶矩和带权重的一阶矩在低浓度时反映红血球的平均速率而在高浓度时反映均方根速率。     

电子束光刻中邻近效应的Monte Carlo模拟

电子束光刻不受衍射效应的限制，具有高分辨率和能产生特征尺寸在100nm以下图形的优点。目前，国际上正在将角度限制散射的投影电子束光刻技术作为21世纪100纳米以下器件大规模生产的主流光刻技术进行重点开发。     

Monte Carlo simulation of the GaAs permeable base transistor

A two-dimensional multiparticle Monte Carlo (MC) method for the solution of the Boltzmann transport equation has been implemented and the results compared with the conventional drift-diffusion equation solution obtained for both a uniformly doped and an n⁺-n-n⁺GaAs permeable base transistor structure. Improved high-frequency performance is predicted by the MC simulation. Two-dimensional boundary conditions for a "regional" MC analysis have been applied to reduce the computer time that would be spent largely in analyzing the device retarding field region and the neutral regions of the device. The dc parameters, I-V characteristics, and unity current gain-frequency (fT) are discussed. In the n⁺-n-n⁺doped structure, a cooling effect was found that significantly enhances the device frequency performance by reducing the satellite valley population of electrons.     

扫描电子显微学中二次电子发射过程的蒙特卡洛模拟

利用蒙特卡洛模拟固体中电子散射轨迹的计算方法，系统地研究了扫描电镜中二次电子信号的发射过程。该模拟电子与固体相互作用的蒙特卡洛模型包含了级联二次电子产生的过程，并且采用光学介电函数方法描述电子的能量损失和相伴的二次电子激发。由于模拟计算可以给出背散射电子和二次电子的绝对产额，以及它们随加速电压和样品的原子序数的变化关系，因此可以用于模拟元素衬度和形貌衬度像。还计算得到了关于二次电子产生和发射的其它分布，并与实验结果作了比较。