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1.
Analytical models of lateral power devices with arbitrary vertical doping profiles in the drift region
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By solving the 2D Poisson's equation, analytical models are proposed to calculate the surface potential and electric field distributions of lateral power devices with arbitrary vertical doping profiles. The vertical and the lateral breakdown voltages are formulized to quantify the breakdown characteristic in completely-depleted and partially-depleted cases. A new reduced surface field (RESURF) criterion which can be used in various drift doping profiles is further derived for obtaining the optimal trade-off between the breakdown voltage and the on-resistance. Based on these models and the numerical simulation, the electric field modulation mechanism and the breakdown characteristics of lateral power devices are investigated in detail for the uniform, linear, Gaussian, and some discrete doping profiles along the vertical direction in the drift region. Then, the mentioned vertical doping profiles of these devices with the same geometric parameters are optimized, and the results show that the optimal breakdown voltages and the effective drift doping concentrations of these devices are identical, which are equal to those of the uniform-doped device, respectively. The analytical results of these proposed models are in good agreement with the numerical results and the previous experimental results, confirming the validity of the models presented here. 相似文献
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Summary A brief review on how to study frustrated spin models by mapping them into generalized percolation models is given. The percolation
models associated to a number of deterministic frustrated models are discussed with particular attention on the properties
of critical clusters.
Paper presented at the I Internatioanl Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994. 相似文献
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采用水介质同轴电极实验装置,开展了μs级充电加压水介质击穿实验研究,并对实验结果进行了分析和讨论,结果表明:在水介质正电极击穿类型的实验中,常压下水介质击穿场强与Martin公式吻合。加压水介质击穿场强随静压的增加而增加,其场强增幅与Mirza定性理论场强增幅的相对差别在5%以内。根据实验结果推导出了更为准确的水介质击穿场强随静压变化的关系式。对水介质加压,将压缩电极表面气泡,减少气泡数目,从而可以提高水介质耐高电压击穿能力。 相似文献
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A simple scaling of bulk laser-induced breakdown threshold for wide band-gap solids is derived on the basis of a recent modification
of the Keldysh photo-ionization model [43, 46]. Contrary to most traditional models, the modification is based on rigorous
energy dependence of reduced effective electron–hole mass. The dependence leads to a specific ionization regime with an extremely
high ionization rate resulting in intensive generation of conduction-band electrons. The regime is characterized by a well-determined
threshold intensity that is proposed to be associated with the threshold of bulk intrinsic laser-induced breakdown (LIB) by
visible and near-infra-red laser radiation. That allows deriving dependence of LIB threshold on laser and material parameters.
The presented model provides explanation for the experimental results on LIB thresholds that have not received theoretical
interpretation. In particular, it reproduces empirical dependence of breakdown threshold on the average inter-atomic spacing
derived from the experimental data. The LIB threshold evaluated from the presented model is very close to experimental data
on bulk LIB by tightly focused beams in wide band-gap solids.
PACS 78.47.+p; 42.50.Hz; 42.50.Ct 相似文献
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采用同轴电极实验装置,在μs级充电时进行了加压乙二醇/水混合液正电极击穿实验,并对实验结果进行了分析和解释,得出结论如下:击穿场强随静压以1/8次幂的关系而增加;击穿场强系数随乙二醇浓度的增加而增加;加压和添加乙二醇对于提高水介质耐高电压击穿的能力具有可叠加性,加压比添加乙二醇更有效;在静压12×105 Pa下乙二醇浓度80%的混合液击穿场强比常压下纯水击穿场强高112.2%。加压提高乙二醇/水混合液击穿场强的主要机制是加压增加了击穿延迟时间。 相似文献
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V. S. Barashenkov L. P. Grachev I. I. Esakov B. F. Kostenko K. V. Khodataev M. Z. Yur’ev 《Technical Physics》2000,45(10):1265-1270
Results are presented from studies of a high-pressure electrodeless breakdown in air at the focus of a standing wave in a high-Q quasi-optical two-mirror resonator pumped by single microwave pulses. In the experiment, the breakdown occurred at the front of the pulse of the resonator field. The breakdown field substantially exceeded the critical level and, under fixed conditions, showed a scatter from pulse to pulse. It is shown that the experimentally found excess in the threshold breakdown field over the critical level is due to the fact that the resonator field increases as a discharge plasmoid forms during breakdown and that the appearance of an electron initiating breakdown in a gas is a random event. 相似文献
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John Preskill 《Nuclear Physics B》1981,177(1):21-59
To analyze the physical consequences of a dynamically broken theory of the weak interactions, we must know how the weak gauge group is aligned in an approximate flavor-symmetry group. For a large class of models, spectral-function sum rules enables us to determine this alignment explicitly. We work out the pattern of the electroweak symmetry breakdown for several sample models. Critical values of weak mixing angles are found at which the breakdown pattern changes discontinously. We compute pseudo-Goldstone boson masses, and find that some models contain unusually light charged or colored pseudo-Goldstone bosons. 相似文献
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B. Hartke 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):57-60
The method of global geometry optimization of atomic and
molecular clusters by evolutionary algorithms is briefly
presented and reviewed. As an exemplary application of a
parallelized implementation of such an algorithm, neutral pure
water clusters are globally optimized. In contrast to previous
studies, the sophisticated and quantitatively reliable TTM2-F
potential is employed. Significant qualitative differences to
the earlier results are found, implicating a breakdown of simple
water models for water clusters of non-trivial size. 相似文献
15.
Experimental results are presented on the changes in the optical characteristics of lithium fluoride induced by an electron
beam with time-varying density and pulse energies close to the threshold for destruction of the material. The spatial distribution
of color centers is investigated, especially near breakdown channels. Mechanisms for nonuniform accumulation of defects are
discussed, along with the fundamental causes of the inhomogeneous energy distributions induced by the high-current electron
beam. Concrete results of calculations of the field intensity distribution in LiF crystals during irradiation are presented,
based on models of “uniform” and nonuniform charging of the sample. An abrupt increase in the electric field intensity is
predicted near the breakdown channel.
Zh. Tekh. Fiz. 68, 53–59 (April 1998) 相似文献
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H. Gündel 《等离子体物理论文集》1981,21(6):393-402
A model of the breakdown in high pressure gases is presented taking into consideration the finite voltage rise time at the discharge electrodes and a finite initial charge carrier density in the gap. Several types of breakdown could be distinguished important for several applications. Thus, the range of existence of high pressure laser discharges at a given preionization density and circuit parameters can be calculated. Moreover, the change in the breakdown characteristics of high pressure gases at high temperatures is explained. This behaviour seems to be important for understanding the physical processes in circuit breaker chambers. 相似文献
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Peter Kuchment 《Waves in Random and Complex Media》2002,12(4):R1-R24
A brief survey on graph models for wave propagation in thin structures is presented. Such models arise in many areas of mathematics, physics, chemistry and engineering (dynamical systems, nanotechnology, mesoscopic systems, photonic crystals etc). Considerations are limited to spectral problems, although references to works with other studies are provided. 相似文献
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Jordan U. Anderson D. Backstrom M. Kim A.V. Lisak M. Lunden O. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2004,32(6):2250-2262
The properties of microwave-induced breakdown of air in narrow metallic slots are investigated, both theoretically and experimentally, with emphasis on factors important for protection against transmission of incident high-power microwave radiation. The key factors investigated are breakdown power threshold, breakdown time, peak-leakage power, and total transmitted energy, as functions of incident pulse shape and power density. The theoretical investigation includes estimates of the electric field intensification in narrow slots and basic breakdown plasma modeling. New results important for application to the high-power microwave field, such as the influence of pulse shape on breakdown time and peak-leakage power, are presented. The experimental investigation comprises a set of slot breakdown experiments at atmospheric pressure, which are analyzed to extract key parameters, such as transmission cross section, breakdown time, peak leakage power, and transmitted energy. The experimental data is compared and shown to be in good agreement with results obtained in the theoretical investigation. 相似文献
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The fluid model is proposed to investigate the gas breakdown driven by a short-pulse(such as a Gaussian pulse) highpower microwave at high pressures.However,the fluid model requires specification of the electron energy distribution function(EEDF);the common assumption of a Maxwellian EEDF can result in the inaccurate breakdown prediction when the electrons are not in equilibrium.We confirm that the influence of the incident pulse shape on the EEDF is tiny at high pressures by using the particle-in-cell Monte Carlo collision(PIC-MCC) model.As a result,the EEDF for a rectangular microwave pulse directly derived from the Boltzmann equation solver Bolsig+ is introduced into the fluid model for predicting the breakdown threshold of the non-rectangular pulse over a wide range of pressures,and the obtained results are very well matched with those of the PIC-MCC simulations.The time evolution of a non-rectangular pulse breakdown in gas,obtained by the fluid model with the EEDF from Bolsig+,is presented and analyzed at different pressures.In addition,the effect of the incident pulse shape on the gas breakdown is discussed. 相似文献