A model for the electric field in lightly doped drain structures

A semi-quantitative model for the lateral channel electric field in LDD MOSFET's has been developed. This model is derived from a quasi-two-dimensional analysis under the assumption of a uniform doping profile. A field reduction factor and voltage improvement, indicating the effectiveness of an LDD design in reducing the peak channel field, are used to compare LDD structures with, without, and with partial gate/drain overlap. Approximate equations have been derived that show the dependencies of the field reduction factor on bias conditions and process parameters. Plots showing the trade-off between, and the process-dependencies of, the field reduction factor/voltage improvement and the series resistance are presented for the three cases. Structures with gate-drain overlap are found to provide greater field reduction than those without the overlap for the same series resistance introduced. This should be considered when comparing the double-diffused and spacer LDD structures. It is shown that gate-drain offset can cause the rise of channel field and substrate current at large gate voltages. This offset is also found to be responsible for nonsaturation of drain current. The model has also been compared with two-dimensional simulation results.     

The static electric field distribution between two semi-infinite circular cylinders: A model for the feed gap field of a dipole antenna

The static electric field distribution in the gap between two solid perfectly conducting semi-infinite cylinders is obtained in terms of a Fourier-Bessel eigenfunction series. For dipole antennas whose cylinder diameter2aand gap length2dare both much less than the operating wavelengthlambda, this field can serve as the quasistatic excitation field in the gap of the dipole. However, the Fourier-Bessel series is slowly convergent. It is transformed into a rapidly convergent series of ultrasphetical polynomials whose weighting function explicitly satisfies the Meixner edge condition. Numerical results are presented graphically for both the axial electric field on the gap surface and the associated potential distribution. Gap ratios ofd/afrom 0.01 to 10.0 are considered and it is shown that asd/a rightarrow 0the solution approaches the two-dimensional solution obtainable by conformal mapping.     

Electron holography study of electric field variations

This paper presents a review of the recent electron holography studies on electric field variation that have been carried out using multifunctional specimen holders. In addition to the standard inner potential analysis, studies on electric field variations around field emission tips have been carried out. The electric field variations caused by ballistic emission in the case of a field emitter made of a TaSi(2) nanowire have been analyzed using electron holography. The charges and electric fields in electrophotographic materials such as toner particles and organic photoconductors have been quantitatively evaluated after equipping the specimen holder with a piezodriving probe to shield the specimens from electron irradiation. The conductivity and electric field variations in the case of Ag-based conductive adhesives have been analyzed by applying an electric current through the holder. Finally, the characteristic charging effect induced by electron irradiation in biological specimens has been studied. It has also been pointed out that under certain experimental conditions, the stationary orbits of electron-induced secondary electrons can be located by electric field visualization.     

Second-order model of membrane electric field induced by alternating external electric fields

With biological cells exposed to ac electric fields below 100 kHz, external field is amplified in the cell membrane by a factor of several thousands (low-frequency plateau), while above 100 kHz, this amplification gradually decreases with frequency. Below 10 MHz, this situation is well described by the established first-order theory which treats the cytoplasm and the external medium as pure conductors. At higher frequencies, capacitive properties of the cytoplasm and the external medium become increasingly important and thus must be accounted for. This leads to a broader, second-order model, which is treated in detail in this paper. Unlike the first-order model, this model shows that above 10 MHz, the membrane field amplification stops decreasing and levels off again in the range of tens (high-frequency plateau). Existence of the high-frequency plateau could have an important impact on present theories of high-frequency electric fields effects on cells and their membranes.     

An analytical model for the internal electric field insubmicrometer MOSFETs

A pseudo-two-dimensional analytical MOSFET model is presented. The channel is divided into source, drain, and junction regions. The source region includes an expression for the carrier-velocity saturation based on the Scharfetter-Gummel formula. The drain region includes an expression for the spread of the lateral field into the bulk. The bulk field in the drain region is described by the radial field from a semicircular drain junction. The junction region describes the voltage drop across a diffused doping profile given an exponential approximation at the junction. The saturation condition is evaluated for both the validity of the gradual channel approximation (GCA) in the source region and carrier-velocity saturation in the drain region. The model elucidates the dependence of the surface field on substrate bias, drain junction depth, and diffusion profile. The model is compared to MINIMOS calculations and found to correlate within 10% for all bias and device combinations of interest for modeling EPROM devices. The computation time of the model is two to three orders of magnitude shorter than full two-dimensional MINIMOS simulations     

A closed-form model of the drain-voltage dependence of the off-state channel electric field in a HEMT with a field plate

The channel-field distribution under the field plate in a high-electron mobility transistor (HEMT) in the off-state is modeled in terms of drain-voltage and physical parameters. Depending upon the drain-voltage and device structure, this distribution can have up to three peaks-one each at the two ends of the field plate and at the drain. It is shown that the complete distribution can be approximated as superposition of triangular distributions, which are analogous to that in the depletion layer of a p-n junction; consequently, the peaks increase as square root of the drain-voltage. The model fits into two-dimensional simulation results and allows estimation of the minimum drain-gate separation, the electric-field reduction, the breakdown-voltage improvement, and critical field for the onset of a parasitic phenomenon in a HEMT with a field plate.     

激光辐照加电场激发对滇稻的育种研究

我们用激光辐照加电场激发处理了滇稻种子，通过室内育秧和田间试验，发现在出苗率，有效分蘖和结实率等方面均优于单纯激光处理的稻种。     

A comparison of Lanczos electric field propagation methods

The authors analyze the losses of a strongly guiding semiconductor rib waveguide Y-junction with the aid of various propagation algorithms based on Lanczos reduction. Although for the example Lanczos procedures adequately describe electric field propagation in the Fresnel approximation, the Helmholtz implementation converges unacceptably slowly. They therefore propose a finite-difference wide-angle approach which employs a power-series expansion of the forward propagation operator. The computational efficiency of the method is comparable to that of the Fresnel formalism with little or no reduction in accuracy from the Helmholtz technique     

An analytical model for the lateral channel electric field in LDDstructures

An analytical model for the lateral channel electric field in lightly doped drain (LDD) MOSFETs is developed from a pseudo-two-dimensional analysis. The model gives a prediction of the channel field when the lightly doped region is both fully depleted and partially depleted. The normal field mobility degradation and variation of the saturation field E_sat with gate voltage have been taken into account in the model. The boundary conditions for determining the pinch-off point L_sat proposed in the model along with the normal field mobility degradation consideration make possible the prediction of the variation of the pinch-off with the gate bias and the maximum value of the electric field E_max . The differences between this model, existing models, and two-dimensional numerical simulations are discussed     

Indoor electric field level prediction model based on theartificial neural networks

A new field strength prediction model for the mobile phone environment is presented. The model is based on the principles of popular feedforward neural networks. Utilizing a new artificial neural network model some important disadvantages of both deterministic and empirical models can be overcome. In order to build the model, extensive field strength measurements were carried out inside two different buildings. The analysis of the model has shown that the proposed model is fast, accurate (on the order of the focal mean measurements uncertainty) and reliable     

Macrocell electric field strength prediction model based upon artificial neural networks

A new macrocell prediction model for mobile radio environment is presented. The use of feedforward artificial neural networks makes it possible to overcome some important disadvantages of previous prediction models, including both deterministic and statistical types. Our sample implementation is based upon extensive electric field strength measurements (in the 900-MHz frequency band) that were carried out in the city of Belgrade using six different test transmitter locations. Comparison between the data obtained by the proposed electric field strength prediction model and independent measurement sets show that the proposed model is sufficiently accurate for use in planning mobile radio systems.     

电场对含空位缺陷硅结构影响的第一性原理研究

用分子动力学模拟和第一性原理计算分析方法,研究电场对含空位缺陷硅结构的影响。分子动力学结果表明,硅(100)晶面处的空位数量,总体随着电场强度的增强而增加。当电场在8.90×10~6 V/cm和1.35×10~7 V/cm之间时,空位数达到最大饱和数值10,并保持稳定。第一性原理计算结果表明,能带结构中的缺陷能级等效于降低价带和导带之间的带隙值,导致空位结构中隧穿电流变大。此外,缺陷能级也会导致空位结构中的静态介电常数变大,从而引起电容-电压特性值变大。     

Practical model for low electric field direct-tunnelling currentcharacteristics in nanometer-thick oxide films

A practical model for direct-tunnelling characteristics at low electric fields in nanometre-thick SiO₂ films is proposed. The model allows for the effective increase in the tunnelling barrier width with a quantum-mechanical consideration of the electron density near the Si-SiO₂ interface. The simulation results coincide well with experimental results     

A new high-voltage electric field instrument for studying sprites

The high-voltage (HV) electric field detector is a new high-voltage, high-impedance, double Langmuir probe instrument designed for stratospheric electric field measurements. In the Sprite Balloon Campaign 2002-2003, this HV instrument was used to measure electric fields between 100 and 200 V/m associated with lightning discharges, which is nearly an order of magnitude higher than previously reported above 30 km in altitude. This increased range is made possible by the availability of new low-leakage HV operational amplifiers. This is a critical instrument, since a large quasi-DC electric field associated with positive cloud-to-ground lightning is a primary component of most sprite generation mechanisms. The difficulty that exists when making electric field measurements in the high-resistance environment of the stratosphere is presented, and how this difficulty is remedied is described. The HV detector is compared to another electric field instrument, the low-voltage detector, used simultaneously on the Sprite Balloon Campaign to verify the accuracy of the HV probes. Finally, a large field perturbation (E/sub z//spl ap/-101 V/m and E/sub x//spl ap/79 V/m) measured by the HV detector during Flight 1, correlated with nearby +15-kA and +53-kA cloud-to-ground strokes, is presented.     

A guided-wave optical electric field sensor with improvedtemperature stability

This paper reports on the study of an electric field sensor based on the Y-cut LiNbO₃ waveguide which has slight temperature dependence. The errors in the electric field measurements due to temperature variations were theoretically studied and the increase in the error with a temperature change of 100 K has been proven to be extremely low, 2.5%. As a technology to achieve high temperature stability, we adopted a new method of attaching optical fibers to a waveguide and a method of suppressing the pyroelectric effect by depositing (ITO) In₂O₃-SnO₃ films onto the Z-faces. The temperature dependence of the fabricated sensor was measured and it was found that the measurement errors in a broad temperature range from -30 to 90°C was ±7% or less     

聚酰亚胺振动膜微型电场传感器

设计并分析了一种新型的以硅为基底、聚酰亚胺为振动膜的微型电场传感器。此种传感器利用了聚酰亚胺耐热、耐腐蚀并具有良好机械性能的特点,采用MEMS技术制造,使其具备体积小、重量轻、功耗低、便于与其他器件集成等特点,而且制作工艺简单,成本较低。本文阐述了此传感器的工作原理,并通过计算机模拟确定了增强信号的方法,同时描述了新型传感器的结构设计和加工工艺过程。     

Analytical expression for electric field between two facing strip electrodes in microchannel

An analytical solution is presented for the electric field between two facing strip electrodes situated in a microchannel, as frequently used in impedance cytometry applications. The measured change in resistance as induced by a 5 /spl mu/m bead moving through the microchannel is in good agreement with the model. It is also demonstrated that the centre sensitivity is maximal for an electrode width equal to /spl sim/56% of the channel height.     

An analytical model for the channel electric field in MOSFET's with graded-drain structures

A simple analytical model for the lateral channel electric field in the drain region of MOSFET's with graded-drain or lightly doped drain structures is presented. The model's results agree well with two-dimensional simulations of the electric field in the drain region. Due to its simplicity, this model gives a better understanding of the mechanisms involved in reducing the electric field in the lightly doped region. Results show the impact of the length and doping concentration, assumed to be Gaussian, of the lightly doped region on the electric field. Effects of the oxide thickness and junction depth are also accounted for. In each case, there is an optimum doping concentration that minimizes the peak electric field.     

Split-operator electric field reflection techniques

The authors have analyzed several approximations for the reflection coefficient of an electric field incident on the interface between two inhomogeneous dielectric media. While existing expressions agree with exact results in certain limits, realistic waveguides with discontinuous refractive index changes are often more accurately modeled by dividing the incoming electric field into segments coinciding with the intervals over which the interface is continuous, and subsequently superimposing the reflection from each segment.<>