Quantum Simulation Study of a New Carbon Nanotube Field-Effect Transistor With Electrically Induced Source/Drain Extension

In this paper, we present the unique features exhibited by a proposed structure of coaxially gated carbon nanotube field-effect transistor (CNTFET) with doped source and drain extensions using the self-consistent and atomistic scale simulations, within the nonequilibrium Green's function formalism. In this novel CNTFET structure, three adjacent metal cylindrical gates are used, where two side metal gates with lower workfunction than the main gate as an extension of the source/drain on either side of the main metal gate are biased, independent of the main gate, to create virtual extensions to the source and the drain and also to provide an effective electrical screen for the channel region from the drain voltage variations. We demonstrate that the proposed structure of CNTFET shows improvement in device performance focusing on leakage current, on–off current ratio, and voltage gain. In addition, the investigation of short-channel effects for the proposed structure shows improved drain-induced barrier lowering, hot-carrier effect, and subthreshold swing, all of which can affect the reliability of CMOS devices.      

Quantum Control of Capture Processes into Localized States of a Quantum Dot

The capture of an electronic wave packet moving in a quantum wire into localized states of a quantum dot by means of LO phonon emission is studied on a quantum kinetic level. In general, if there is more than one bound state the capture process leads to the creation of a superposition of these states resulting in an oscillating wave packet inside the dot. It is shown that these oscillations can be efficiently controlled by means of the capture of a second wave packet moving towards the dot from the other side. Depending on the phase of the oscillations at the time of arrival of the second wave packet the amplitude of the spatial oscillations is either reduced or enhanced.     

Simulation of Spin-Qubit Quantum Dot Circuit with Integrated Quantum Point Contact Read-Out

We provide a physical analysis of the charging and detection of the first few electrons in a laterally-coupled GaAs/AlGaAs quantum dot (LCQD) circuit with integrated quantum point contact (QPC) read-out. Our analysis is based on the numerical solution of the Kohn-Sham equation incorporated into a three-dimensional self-consistent scheme for simulating the quantum device. Electronic states and eigenenergy spectra reflecting the particular LCQD confinement shape are obtained as a function of external gate voltages. We also derive the stability diagram for the first few electrons in the device, and obtain excellent agreement with experimental data.     

Quantum Logic Circuits and Optical Signal Generation for a Three-Qubit, Optically Controlled, Solid-State Quantum Computer

We analyze the preparation of an experimental demonstration for a three-qubit, optically controlled, solid-state quantum computational system. First, using a genetic programming approach, we design quantum logic circuits, specifically tailored for our computational model, which implement a three-qubit refined Deutsch–Jozsa algorithm. Aiming at achieving the shortest possible computational time, we compare two design strategies based on exploiting two different sets of entangling gates. The first set comprises fast approximations of controlled-phase gates, while in the second case, we exploit arbitrary entangling gates with gate computational times shorter than those of the first set. Then, considering some recently proposed material implementations of this quantum computational system, we discuss the generation of the near-midinfrared, multiwavelength and picosecond optical pulse sequences necessary for controlling the presented quantum logic circuits. Finally, we analyze potential sources of errors and assess the impact of random fluctuations of the parameters controlling the entangling gates on the overall quantum computational system performance.      

量子点发光材料在多色照明上的应用

半导体量子点作为一种最新型的荧光材料,与传统的荧光材料相比具有多种优势.由于量子局域效应,单一种类的量子点材料就能够通过改变其尺寸来产生不同颜色的单色光.本文简要描述了量子点材料的发光特性及其在照明光源器件中的应用前景.文中给出了CdSe量子点材料的制备方法和其发光特性,探讨了如何将不同尺寸的CdSe量子点复合在一起来获得多色照明器件.     

3D numerical modeling of Quantum Dot using homotopy analysis

The 3D numerical modeling of nanoscale InGaAs quantum dot is developed and the characteristics of the device are presented. The exact potential and energy profile of the Quantum Dot are computed by obtaining the solution of 3D Poisson and Schrodinger equations using homotopy analysis. The dark current is estimated by considering the Quantum Dot density, applied voltage, length of quantum dot array, number of quantum dot array and temperature. The results obtained show that the dark current is strongly influenced by Quantum Dot density and applied voltage. The developed model is physics based one and overcomes the limitations of the existing analytical models. The model is validated by comparing the results obtained with the existing models.     

Processing and Properties of Ferroelectric Pb(Zr,Ti)O3/Silicon Carbide Field-Effect Transistor

Metal-ferroelectric-(insulator)-semiconductor MF(I)S structures have been fabricated and the properties of pulsed laser-deposited PZT/Al₂O₃ gate stacks have been studied on n- and p-type 4H-SiC. Among several polytypes of SiC, 4H-SiC is considered as the most attractive one because of its wider bandgap (E _g ? 3.2 eV) as well as higher and more isotropic bulk mobility than other polytypes. Single PZT phase without a preferred orientation was confirmed by x-ray diffraction. The interface trap densities N _IT, fixed oxide charges Q _F, and trapped oxide charges Q _HY have been estimated by C-V curves with and without photo-illuminated measurements at room temperature. It is found that the charge injection from SiC is the dominant mechanism for C-V hysteresis. Importantly, with PZT/Al₂O₃ gate stacks, superior C-V characteristics with negligible sweep rate dependence and negligible time dependence under the applied bias were obtained compared to PZT directly deposited on SiC. The MFIS structures exhibited very stable capacitance-voltage C-V loops with low conductance (<0.1 mS/cm², tan δ ～ 0.0007 at 400 kHz) and memory window as wide as 10 V, when 5 nm-thick Al₂O₃ was used as a high bandgap (E _g ～ 9 eV) barrier buffer layer between PZT (E _g ～ 3.5 eV) and SiC (E _g ～ 3.2 eV). The structures have shown excellent electrical properties promising for the gate stacks as the SiC field-effect transistors (FETs). Depletion mode transistors were prepared by forming a Pb(Zr_0.52Ti_0.48)O₃/Al₂O₃ gate stack on 4H-SiC. Based on this structure, ferroelectric Pb(Zr,Ti)O₃ (PZT) thin films have been integrated on 4H-silicon carbide (SiC) in a SiC field-effect transistor process. Nonvolatile operation of ferroelectric-gate field-effect transistors in silicon carbide (SiC) is demonstrated.     

Signatures of a Discrete Level Spectrum and Dynamical Tunneling in the Conductance of a Large Open Quantum Dot

We simulate transport in large, strongly-open, quantum dots, which typically would be viewed as lying well within the semiclassical regime for which all energy levels can be assumed to be broadened. Contrary to this assumption, we find that resonances, which can be associated with individual eigenstates, can persist even under these conditions. Their presence yields regular fluctuations in the low temperature conductance which persist in the presence of a moderately-disordered dot potential and can be observed experimentally. Examining the resonant wave functions, we typically find them to be scarred by regular periodic orbits which are classically inaccessible from the leads. As such, our results suggest that dynamical phase-space tunneling may play a more generic role in transport through mesoscopic structures than has thus far been appreciated.     

数字棒位显示系统探测器缺陷分析及改进

针对AP1000依托项目棒位指示系统探测器所发现的问题进行分析,并通过后续改进制造工序,运用相关标准对关键工艺进行质量控制和验收。结果表明:经过工艺改进和标准使用控制,可以消除缺陷,并在后续制造过程中防止重复发生,取得良好效果;同时,也为该类设备在后续制造和质量管理提供经验反馈和良好借鉴。     

Analysis of Hot-Carrier Luminescence for Infrared Single-Photon Upconversion and Readout

We propose and analyze a new method for single-photon wavelength up-conversion using optical coupling between a primary infrared (IR) single-photon avalanche diode (SPAD) and a complementary metal oxide semiconductor (CMOS) silicon SPAD, which are fused through a silicon dioxide passivation layer. A primary IR photon induces an avalanche in the IR SPAD. The photons produced by hot-carrier recombination are subsequently sensed by the silicon SPAD, thus, allowing for on-die data processing. Because the devices are fused through their passivation layers, lattice mismatch issues between the semiconductor materials are avoided. We develop a model for calculating the conversion efficiency of the device, and use realistic device parameters to estimate up to 97% upconversion efficiency and 33% system efficiency, limited by the IR detector alone. The new scheme offers a low-cost means to manufacture dense IR-SPAD arrays, while significantly reducing their afterpulsing. We show that this high-speed compact method for upconverting IR photons is feasible and efficient.     

Optical and Electrical Properties of Colloidal Quantum Dots in Electrolytic Environments: Using Biomolecular Links in Chemically-Directed Assembly of Quantum Dot Networks

The threshold of the absorption spectra of colloidal cadmium sulfide (CdS) quantum dots in electrolytic solutions is shown to shift as the concentration of the electrolyte is varied. The shift in the absorption threshold as a function of the electrolytic concentration is given by electrolytic screening of the field caused by the intrinsic spontaneous polarization of these würtzite quantum dots. These electrolyte-dependent absorption properties are compared with Fermi-level tuning in carbon nanotubes in electrolytic environments.Moreover, concepts for integrating such colloidal quantum dots in high density networks with biomolecular links are discussed. Such biomolecular links are used to facilitate the chemically-directed assembly of quantum dots networks with densities approximating 10¹⁷ cm⁻³.     

Eigenstate Selection in Open Quantum Dot Systems: On the True Nature of Level Broadening

We show that transport in open quantum dots can be mediated by single eigenstates, even when the leads allow several propagating modes. The broadening of these states, generally localized in the interior, can be virtually independent of lead width. As such, the Thouless argument, invoked to suggest that all states should be unresolvable under these conditions, can in fact fail. Thus, any transport theory based on such assumptions (in particular, random matrix theory) must be called into question, as the fluctuations produced by these states can in fact dominate the conductance. These trapped states also produce interesting and potentially useful effects in coupled dot systems as well.     

双注入结型场效应晶体管直流特性分析

对新型双注入结型场效应器件的直流特性进行了较详细的分析 ,得出直流特性的解析表达式 ,证明这种器件由电压控制导电能力 ,具有较大的电流输出、功率输出和输入阻抗 ,是一种兼有双极器件和场效应器件特点的新型电子器件。     

半导体量子点电致发光器件用于航空舱内照明的可行性研究

本文分析了半导体量子点电致发光器件用于航空舱内照明的可行性。根据国内外相关资料,讨论了航空舱内照明的夜视兼容性要求,说明了航空舱内照明系统的发展现状,对半导体量子点电致发光器件以及夜视兼容相关指标的测试方法进行了阐述。本文一致认为半导体量子点电致发光器件将来会替代现用发光光源,为航空舱提供一般照明。     

给水泵液力偶合器改造后的运行经济性

给水泵是火电厂辅机中能耗最高的设备,耗电量占厂用电的30%~35%,降低给水泵电耗对降低厂用电率作用显著。结合给水泵采用液力偶合器的改造,用实例对母管制给水系统如何提高给水泵运行的经济性和可靠性进行了分析论证。     

PLC系统运行故障分析

手动方式是电路的一种控制形式,通过主令电器人为地控制负载。直给方式是甩开控制器件,使能源直接作用于负载。常见的有直给电磁阀和直给电动机。两种方式的共同点是在设备维修中,可用于判断负载的故障。     

双管箝位正激变换器的无源无损耗缓冲电路分析

双管箝位正激变换器是一种常用的电路拓朴。本文详尽地分析了一种双管箝位正激变换器的无源无损耗缓冲电路的工作原理及工作过程,指出正确选择缓冲电路的参数的理论依据。     

新型阻抗继电器的运行特性分析

本方从I_0极化接地电抗特性入手讨论了几种新型距离继电器的运行特性。最后将其重点放在新型综合比相式距离继电器的仿真计算研究上面[1]。对双侧供电线路,在被保护线路上各点经过过渡电阻短路以及保护分别处于送端和受端时,所存在的超越和缩小范围的情况。这些分析结果提供的结论使我们加深了对这些继电器的认识,对今后的继续研究是有益的。     

无刷直流电动机运行特性的分析

介绍了无刷直流电动机的两种方案，列出了系统的基本方程式，并对其运行特性进行了分析。     

新型整流变压器及其滤波系统的运行参数特性分析

新型整流变压器及其滤波系统由网侧、阀侧绕组,独立滤波绕组及与之相连的滤波器组构成,其特殊的滤波支路能够在滤波和无功补偿的同时改善变压器的运行特性。首先推导以谐波抑制因子为表达方式的谐波电流抑制模型以考察谐波传递情况;然后构建网侧绕组电流和负载电流之间的数学关系,藉此研究无功补偿特性,并分析相关的运行参数;之后建立阀侧电压与网侧电压的数学关系,以研究滤波器对阀侧电压的影响。理论分析表明,新型整流变压器及其滤波系统可以有效抑制谐波,降低网侧电流和视在功率,提高网侧功率因数并增加负载电压。实际应用在工业直流供电系统中的新型整流变压器的现场实测结果,验证了理论分析的正确性。该文更全面地揭示了新型整流变压器能改善整流系统的运行特性,所推导的数学模型将为新型整流变压器在降噪节能等方面的进一步研究提供理论依据。