Analytical modeling of subthreshold swing in undoped trigate SOI MOSFETs

A new analytical model for the subthreshold swing of nanoscale undoped trigate silicon-on-insulator metal–oxide–semiconductor field-effect transistors (MOSFETs) is proposed, based on the channel potential distribution and physical conduction path concept. An analytical model for the potential distribution is obtained by solving the three-dimensional (3-D) Poisson’s equation, assuming a parabolic potential distribution between the lateral gates. In addition, mobile charges are considered in the model. The proposed analytical model is investigated and compared with results obtained from 3-D simulations using the ATLAS device simulator and experimental data. It is demonstrated that the analytical model predicts the subthreshold swing with good accuracy for different lengthes, thicknesses, and widths of channel.     

Two-dimensional modeling of subthreshold current and subthreshold swing of double-material-gate (DMG) strained-Si (s-Si) on SGOI MOSFETs

The present paper proposes the surface potential based two-dimensional (2D) analytical models of subthreshold current and subthreshold swing of nanoscale double-material-gate (DMG) strained-Si (s-Si) on Silicon-Germanium-on-Insulator (SGOI) MOSFETs. The surface potential expression has been directly taken from our previous reported work. The effect of various device parameters on subthreshold current and swing like Ge mole fraction, Si film thickness, gate-length ratio and various combinations of control/screen gate work-functions have been discussed. The validity of the present 2D model is verified by using ATLAS^TM, a 2D device simulator from Silvaco.     

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.     

2D Modeling of nanoscale DG SOI MOSFETs in and near the subthreshold regime

We have developed a 2D model for double-gate SOI MOSFET based on a solution of the Laplacian for the device body utilizing conformal mapping techniques. The model yields explicit expressions for the subthreshold and near-threshold electrostatics of the device, including the perpendicular electrical field and the potential distributions along the silicon/insulator interfaces and at the center gate-to-gate axis. From these expressions, we derive information on the threshold conditions, the potential barrier topography, and the electron density distribution in the device under different biasing conditions. This model constitutes a framework for very precise, scalable, compact models of nanoscale MOSFETs.     

An analytical model of threshold voltage for short-channel double-material-gate (DMG) strained-Si (s-Si) on Silicon-Germanium-on-Insulator (SGOI) MOSFETs

In this paper, an analytical short-channel threshold voltage model is presented for double-material-gate (DMG) strained-Si (s-Si) on Silicon-Germanium-on-Insulator (SGOI) MOSFETs. The threshold voltage model is based on the “virtual cathode” concept which is determined by the two-dimensional (2D) channel potential of the device. The channel potential has been determined by solving 2D Poisson’s equation with suitable boundary conditions in both the strained-Si layer and relaxed Si_1?x Ge _x layer. The effects of various device parameters like Ge mole fraction, Si film thickness, SiGe thickness and gate-length ratio have been considered on threshold voltage. Further, the drain induced barrier lowering (DIBL) has also been estimated. The validity of the present 2D analytical model is verified by using ATLAS?, a 2D device simulator from Silvaco.     

3D Monte Carlo Modeling of Thin SOI MOSFETs Including the Effective Potential and Random Dopant Distribution

We use the effective potential to include quantum mechanical effects in thin SOI MOSFETs simulated with 3D Monte Carlo. We explore the role of discrete dopant distributions on the threshold voltage of the device within the framework of the effective potential by examining the current-voltage behavior as well as the electron distributions within the device. We find that simulations with the effective potential produce a similar shift in current as classical simulations when the dopants are considered to have a random discrete distribution instead of a uniform distribution.     

Compact 2D modeling and drain current performance analysis of a work function engineered double gate tunnel field effect transistor

The ongoing trend of device dimension miniaturization is attributed to a large extent by the development of several non-conventional device structures among which tunneling field effect transistors (TFETs) have attracted significant research attention due to its inherent characteristics of carrier conduction by built-in tunneling mechanism which in turn mitigates various short channel effects (SCEs). In this work, we have, incorporated the innovative concept of work function engineering by continuously varying the mole fraction in a binary metal alloy gate electrode along the horizontal direction into a double gate tunneling field effect transistor (DG TFET), thereby presenting a new device structure, a work function engineered double gate tunneling field effect transistor (WFEDG TFET). We have presented an explicit analytical surface potential modeling of the proposed WFEDG TFET by the solving the 2-D Poisson’s equation. From the surface potential expression, the electric field has been derived which has been utilized to formulate the expression of drain current by performing rigorous integration on the band-to-band tunneling generation rate over the tunneling region. Based on this analytical modeling, an overall performance comparison of our proposed WFEDG TFET with its normal DG TFET counterpart has been presented in this work to establish the superiority of our proposed structure in terms of surface potential and drain current characteristics. Analytical results have been compared with SILVACO ATLAS device simulator results to validate our present model.     

Simulation and Characterization of Piezoelectric Micromachined Ultrasonic Transducers (PMUT's) Based on PZT/SOI Membranes

Piezoelectric micromachined ultrasonic transducers for airborne and immersed applications working in the frequency range from 20 kHz in liquid to 750 kHz in air have been fabricated and characterized, as well as simulated by finite element modelling. The basic element consisted of a oxidized and platinized silicon membrane coated with a 2 μm thick (100)-textured Pb(Zr,Ti)O₃ (PZT) thin film deposited by sol-gel techniques. SOI wafers have been applied to obtain a good definition of the silicon part of the membrane. The unclamping of the silicon membrane at the border increases drastically the coupling factor. For unclamped structures the membranes completely covered with top electrode show the highest coupling coefficient (k² = 5.6%). Immersed (in Fluorinert?) membranes show 7 times smaller quality factor, while the coupling factor k² remains the same. The obtained structures were enough sensitive to detect acoustic waves in air and in liquid emitted from the same type of elements at a distance of 20 and 2 cm, respectively. Good agreement between the experimental results (membrane deflection, admittance in air and in liquid) and FEA simulations has been obtained.     

一种数字旋变接口电路的改进设计

数字旋变转换器SXZ与PC机的接口通常采用8255等分立元件设计。这种电路存在占用I／O端口资源和使用分立元件多,PCB板面积较大等缺点。本文采用VHDL,改进设计了一种多通道的12位接口电路,实际应用表明,该电路具有更好的性价比,如尺寸小,易维护和抗干扰性强等。     

Analytical synthesis of voltage‐mode even/odd‐nth‐order differential difference current conveyor and fully differential current conveyor II‐grounded resistor and capacitor universal filter structures

A complete definition of an odd/even‐nth‐order notch or band‐reject filter transfer function is presented. Based on the differences between the input voltage and (i) an nth‐order high‐pass; (ii) a traditional nth‐order notch; and (iii) an nth‐order all‐pass filtering transfer function, a systematic method has been proposed to derive a universal filter structure that can realize voltage‐mode odd/even‐nth‐order low‐pass, band‐pass, high‐pass, all‐pass and traditional notch filters. The intrinsic capability of voltage‐mode addition and subtraction of the two active elements, differential difference current conveyors and fully differential current conveyors, is used to advantage in the aforementioned synthesis procedure. Based upon the definition of an nth‐order notch or band‐reject filter transfer function proposed in this paper, the aforementioned universal one has been further extended to the newly defined nth‐order band rejection filter. The voltage and current tracking errors of the two active elements are compensated by varying the resistances of the proposed filter. Filtering feasibility, stability, component sensitivities, linear and dynamic ranges, power consumption, and noise are simulated using H‐Spice with 0.35 µm process. Compared to some of the recently reported universal biquads, the new one is shown to enjoy the lowest component sensitivities and the best output accuracy for all‐pass signals. Moreover, Monte Carlo and two‐tone tests for intermodulation linearity simulations are also investigated. Copyright © 2014 John Wiley & Sons, Ltd.     

Optimization of different structural parameters of GeSn/SiGeSn Quantum Well Infrared Photodetectors (QWIPs) for low dark current and high responsivity

Dark current and responsivity are two important parameters of quantum well infrared photodetectors (QWIPs). An optimization approach is applied herein to achieve low dark current along with high responsivity for a GeSn/SiGeSn QWIP. The dark current is reduced by varying different physical parameters of well and barrier, operating temperature and bias voltage of the QWIP. To optimize the QWIP, the detectivity is calculated. The results show that the optimally designed GeSn/SiGeSn QWIP can achieve a low dark current of 2.35 pA at 2 V with a peak responsivity of 1.24 A/W at 4.3 µm and a high detectivity of 3.47?×?10¹² cm · Hz^1/2 W^?1 at 2 V and 77 K. Finally, the frequency response of the optimally designed GeSn/SiGeSn QWIP device is estimated. The theoretically predicted higher detectivity with respect to previously reported SiGe/Si QWIPs and GeSn/SiGeSn interband QWIPs indicates a promising future for GeSn/SiGeSn intersubband QWIPs.

     

GW5-35/110D(W)户外高压隔离开关的结构特点

介绍GW5-35/110高压隔离开关的结构性能特点和技术参数。由于采用子多路先进工艺和安装方式，所以在至孟加拉国的出口任务中，既保证了产品质量，又使用户有多种安装要求的选择余地。     

光纤电流互感器噪声特征及建模方法研究

针对光纤电流互感器(FOCT)的随机噪声问题,借鉴光纤陀螺(FOG)的性能分析方法,分析FOCT的结构及原理,系统地探讨FOCT随机噪声的种类、噪声误差因素及噪声误差抑制措施.结合FOCT噪声所体现出的时域相干性及频域特征,引入Allan方差分析法及建模理论,辨识并量化FOCT的各项噪声误差,全面地评价FOCT性能.Allan方差分析法及建模理论在FOCT数据处理中的应用结果表明,FOCT输出数据中体现了角度随机游走、偏值不稳定性等不同特征的随机噪声,同时证明了Allan方差噪声建模理论在FOCT噪声特征分析方面的可行性.     

光纤电流互感器噪声特征及建模方法研究

针对光纤电流互感器（FOCT）的随机噪声问题,借鉴光纤陀螺（FOG）的性能分析方法,分析FOCT的结构及原理,系统地探讨FOCT随机噪声的种类、噪声误差因素及噪声误差抑制措施。结合FOCT噪声所体现出的时域相干性及频域特征,引入Allan方差分析法及建模理论,辨识并量化FOCT的各项噪声误差,全面地评价FOCT性能。Allan方差分析法及建模理论在FOCT数据处理中的应用结果表明,FOCT输出数据中体现了角度随机游走、偏值不稳定性等不同特征的随机噪声,同时证明了Allan方差噪声建模理论在FOCT噪声特征分析方面的可行性。     

GP/NiOOH/Ni(OH)_2的制备及电化学性能

用化学沉积法制备石墨烯(GP)/Ni OOH/Ni(OH)2多层次多孔复合材料。SEM分析发现:Ni OOH/Ni(OH)2在石墨烯表面形成多孔结构,负载了多孔Ni OOH/Ni(OH)2的石墨烯又进行堆积。复合材料的循环伏安测试表现出典型的赝电容特性,比电容高于纯Ni OOH/Ni(OH)2。石墨烯与Ni OOH/Ni(OH)2的配比对电化学性能影响较大,样品GP/Ni-30(石墨烯为0.1 g,1 mol/L Ni SO4为30 ml)的比电容在电流为2 A/g、10 A/g电压为0~0.45 V时分别为2 178 F/g和1 444 F/g。     

Growth Stages of Sol-Gel Derived PZT(30/70) on Pt/Ti/SiO 2 as Shown by SPM (PFM and Topography)

The integration of PZT into devices based on silicon is of great interest for the further miniaturisation of sensors and actuators and their integration into MEMS devices. PZT is the material of choice for these applications due to it's good piezoelectric properties. When PZT is produced by sol-gel the material undergoes a series of transformations. After the initial drying stage the sol transforms into the non-ferroelectric pyrochlore phase. Upon further heat treatment the ferroelectric perovskite phase is formed. A single layer (ca. 70nm thick) film of PZT has been deposited onto highly [111] orientated Pt. The degree of transformation from the pyrochlore phase to the perovskite phase has been recorded using XRD and a variety of scanning probe techniques, including Piezoresponse force microscopic (PFM) and contact mode topographic analysis. A map of the surface topography and the PFM image show variations in both topography and distribution of piezoelectric regions as the perovskite/pyrochlore ratio changes. The method by which the changes occur can be explained by the nucleation of perovskite phase from the pyrochlore phase. The range of temperatures examined were 400 to 530, the sample being left at each temperature for 5 minutes. It was found that fully transformed perovskite PZT was produced at 530C. The XRD pattern for the sample shows that it is [111] orientated.     

GW5-35/110D(W)户外高压隔离开关的结构特点

介绍GW5－35／110高压隔离开关的结构性能特点和技术参数。由于采用了多种先进工艺和安装方式，所以在至孟加拉国的出口任务中，既保证了产品质量，又使用户有多种安装要求的选择余地。     

Structural and Dielectric Properties of Sol-Gel Derived PLZT (x/60/40)

Polycrystalline samples of (Pb_1-zLa_z)(Zr_0.60Ti_0.40)_1-z/4O₃ (where z = 0.00, 0.05, 0.09, 0.12, 0.14 mol %) (abbreviated as PLZT) were synthesized through acetate-alkoxide sol-gel route. The formation and existence of different crystallographic phases as a function of z was checked through X-ray, TEM, SEM and dielectric studies. The diffuse phase transition (DPT) was observed in PLZT with higher concentration of La (i.e., for z = 0.00 to 0.12), but for z = 0.14, the compound did not show any phase transition.