Modeling Fully Depleted SOI MOSFETs in 3D Using Recursive Scattering Matrices

As the semiconductor industry pushes towards ever decreasing device sizes, the need for an efficient yet accurate simulation method increases. We present a different approach to modeling ultra small semiconductor devices through the use of recursive scattering matrices. This approach is a completely quantum mechanical approach in three dimensions, yet does not suffer from excessive computation time or resources. While the transport in most small semiconductor devices is typically 2D in nature, with a 3D model we are capable of incorporating the interaction of the 3D modes in the contacts with the 2D modes in the active regions. We demonstrate this approach by presenting results for a short channel fully-depleted SOI (Silicon On Insulator) MOSFET. We present results using both hardwall potentials and self-consistent potentials as calculated through the use of an iterative Poisson solver.     

Unity gain and nonunity gain quantum teleportation

We investigate continuous variable quantum teleportation. We discuss the methods presently used to characterize teleportation in this regime, and propose an extension of the measures proposed by Grangier and Grosshans , and Ralph and Lam . This new measure, the gain normalized conditional variance product M, turns out to be highly significant for continuous variable entanglement swapping procedures, which we examine using a necessary and sufficient criterion for entanglement. We elaborate on our recent experimental continuous variable quantum teleportation results , demonstrating success over a wide range of teleportation gains. We analyze our results using fidelity; signal transfer, and the conditional variance product; and a measure derived in this paper, the gain normalized conditional variance product.     

Phonon exacerbated quantum interference effects in III-V nanowire transistors

In recent years, a great deal of attention has been focused on the development of quantum wire transistors as a means of extending Moore’s Law. Here we present, results of fully three-dimensional, self-consistent quantum mechanical device simulations of InAs tri-gate nanowire transistor (NWT). The effects of inelastic scattering have been included as real-space self-energy terms. We find that the position of dopant atoms in these devices can lead a reduction in the amount of scattering the carriers experience. We find that the combination of deeply buried dopant atoms and the high energy localization of polar optical phonon processes allow devices to recover their ballistic behavior even in the presence of strong inelastic phonon processes. However, we find that dopant atoms close to the source-channel interface cause severe quantum interference effects leading to significant performance reduction.     

Application of the R-matrix method in quantum transport simulations

The paper gives an overview of recently developed method for effective quantum transport simulations in nanoscale electronic devices. In the present formulation the device is treated as a set of independent close subsystems with appropriate low-dimensional basis representations. In continuous transport models, the local R-matrix basis makes it possible to avoid discretization of the device area and achieve a much higher numerical accuracy with a lower computational burden compared to common grid schemes. Furthermore, the local basis representation provides a suitable framework for studying ionized impurity scattering by adjusting the shape of the device elements and their internal coordinate representation. Non-equilibrium current carrying electronic states are constructed by a recursive propagation scheme such that the major portion of the computation time scales linearly with the device volume. As an illustration, we apply the method to study ionized impurity scattering in a short Si channel.     

数据通信测试仪表的应用

通过近几年的发展建设，在电力通信网中，PDH、SDH、ATM等数字通信技术已大量使用。对数字通信设备进行维护，必须采用先进的测试仪器仪表对故障进行准确定位，以尽快恢复通信电路，确保电力通信的快速、畅通。在设备的维护中，不仅要掌握设备的工作原理，熟悉信号的流程，更要掌握测试仪表的各种告警指示的含义，才能对故障进行准确定位。为此本文介绍了数据通信测试仪表的功能及使用该仪表测试数据接口的方法和注意事项。     

Error models for long-distance qubit teleportation

A recent proposal for realizing long-distance, high-fidelity qubit teleportation is reviewed. This quantum communication architecture relies on an ultrabright source of polarization-entangled photons plus a pair of trapped-atom quantum memories, and it is compatible with long-distance transmission over standard telecommunication fiber. Models are developed for assessing the effects of amplitude, phase, and frequency errors in the entanglement source, as well as fiber loss and imperfect polarization restoration, on the throughput and fidelity of the system.     

量子信息学的理论基础与研究进展

量子信息学是物理学与信息学交叉而形成的一门新兴学科。论述了其建立的理论基础——量子态的纠缠现象,介绍了量子计算机、量子密钥、量子隐形传态等相关高新技术,分析了今后的研究方向,以期对该学科有全面的了解。     

Use of the scattering matrix for device simulations

The use of the quantum mechanical scattering matrix is a time proven method for determining the transport probability for an electron wave in a nanostructure. When coupled with the Landauer formalism, it provides a valuable approach for simulation of semiconductor devices. Here, we discuss a numerically stable method to solve this transmission problem in a recursive manner. It is easily extended to dissipative and far from equilibrium situations. We also discuss the use of scattering matrices in photo excitation of nanostructures.     

General purpose telemetry for analog biomedical signals

The results presented show that the telemetry system described is convenient for transferring analog biomedical signals for a wide range of physiological parameters, even with low-cost standard communication media. The system developed is independent of the types and models of the signal-generating medical devices and is able to communicate worldwide over a broad range of communication medias. The results also show that there are differences in the transmission capacity among the communication media. These practical as well as theoretical differences are important for proper selection of communication devices. Anticipated activity in the field of communication technology (devices and protocols) towards higher data rates and lower costs is expected to further increase system performance     

Can silicon FinFETs satisfy ITRS projections for high performance 10 nm devices?

We utilize a fully self-consistent quantum mechanical simulator based on CBR method to optimize 10 nm FinFET devices to meet ITRS projections for High Performance (HP) logic technology devices. Fin width, gate oxide thickness, and doping profiles are chosen to reflect realistic values. We find that the device on-current approaching the value projected by ITRS for HP devices can be obtained using unstrained conventional (Si) channel. Our simulation results also show that quantum nature of transport in ultra small devices significantly enhances the intrinsic switching speed of the device. In addition, small signal analysis has been performed. Sensitivity of device performance to the process variation at room temperature has also been investigated.     

Effect of elastic processes and ballistic recovery in silicon nanowire transistors

Scaling of silicon devices is fast approaching the limit where a single gate may fail to retain effective control over the channel region. Of the alternative device structures under focus, silicon nanowire transistors (SNWT) show great promise in terms of scalability, performance, and ease of fabrication. Here we present the results of self-consistent, fully 3D quantum mechanical simulations of SNWTs to show the role of surface roughness (SR) and ionized dopant scattering on the transport of carriers. We find that the addition of SR, in conjunction with impurity scattering, causes additional quantum interference which increases the variation of the operational parameters of the SNWT. However, we also find that quantum interference and elastic processes can be overcome to obtain nearly ballistic behavior in devices with preferential dopant configurations.     

Higher harmonics and ac transport from time dependent density functional theory

We report on dynamical quantum transport simulations for realistic molecular devices based on an approximate formulation of time-dependent Density Functional Theory with open boundary conditions. The method allows for the computation of various properties of junctions that are driven by alternating bias voltages. Besides the ac conductance for hexene connected to gold leads via thiol anchoring groups, we also investigate higher harmonics in the current for a benzenedithiol device. Comparison to a classical quasi-static model reveals that quantum effects may become important already for small ac bias and that the full dynamical simulations exhibit a much lower number of higher harmonics. Current rectification is also briefly discussed.     

An electron's spin--Part II

In Part I of this article, we introduced the notion of encoding binary bit information in the spin polarization of a single electron confined in a quantum dot and placed in a magnetic field. The spin polarization becomes bistable in a magnetic field and the spin can point either parallel to the field or antiparallel to it. These two polarizations encode the classical binary bits 0 and 1. We showed that since the bits can be switched by simply flipping the electron's spin without physically moving the electron in space and causing a current, the energy dissipated during the bit flip operation could be made very small. In Part II we discuss the notion of using a single electron's spin as a quantum bit (or qubit) that represents information in quantum computers. Just as spin is superior to charge as a vehicle to host classical bit information in classical computers it turns out that spin is superior to charge to host quantum information as well. That is why spin-based quantum information processing is gradually becoming the staple of scalable solid state versions of quantum computers.     

水平分层土壤中点电流源格林函数的递推算法

分层土壤媒质中点电流源的格林函数是接地系统暂态计算的基础。但由于多层土壤的复杂性，其格林函数极为复杂，不易手工推导。该文通过建立合理的格林函数的数据结构，提出了一种适用于水平分层土壤的格林函数的递推方法。根据这种方法，可以通过计算机程序得到水平分层土壤中每一层的格林函数的表达式，避免了手工推导格林函数带来的繁琐，保证了公式的正确性。将结果代入边界条件方程，方程成立，证明了程序推导得到的格林函数的正确性。推导结果可以直接用于接地系统的数值计算。此方法将大大提高地网接地特性的计算效率。     

Modelling surface effects in nano wire optoelectronic devices

Recent research on optoelectronic devices focuses on nano structuring which is expected to improve the performance and reduce the production costs of light emitting diodes for lighting purposes and solar cells, for instance. Structuring on the sub-micrometer scale increases the surface with respect to the active volume so that surface effects become crucial for the device performance. In this work we demonstrate the computational modelling of nano structured optoelectronic devices to complement the experiment. The implementation of the simulation model considers surface effects in these devices using a true area box method discretization. The derived surface models are applied on the self-consistent simulation of nano wire quantum disk light emitting diodes. By the computational study we demonstrate that the surface physical effects are critical for the performance of nano-structured optoelectronic devices and that surface recombination can lead to a low efficiency.     

Study of RF Linearity in sub-50 nm MOSFETs Using Simulations

We investigate the linearity performance of dual-gate and fully-depleted silicon-on-insulator MOSFETs through use of 2D computer simulations, which take into account quantum mechanical considerations and non-equilibrium transport effects. We show that DG MOSFET is superior not only in terms of g _m /I _d characteristics, central to analog performance, but also in terms of linearity performance, by up to 5 dBm, in most operating conditions. Linearity figures of devices considered in this work range from ?10 to ?20 dBm, which answer the needs of mobile communication standards currently in use. We also observe that, when properly scaled, bulk MOSFETs display competitive analog performance and have third-order intercept figures very similar to SOI device. We can identify, through simulation experiments, that quantum mechanical effects have positive impact on linearity, while non-equilibrium conditions lower linearity performance. With increasing drain bias, we find that linearity saturates at a moderately low voltage (～1 V) in all devices.     

Photonics

Just as the beginnings of electrical engineering came before the discovery of the electron, A. G. Bell's demonstration of the photophone-the granddaddy of photonics experiments in the context of communications-came before the era of the photon. History, like everyday life, abounds with proof that one can do a lot with elements of the natural world without fully understanding them. But better understanding of nature's fundamentals, a worthy end in itself, often unlocks a world of applications, and photonics technology is hot on the heels of electronics in proving that again. The paper reviews the development of photonics technology such as the the use of quantum mechanical devices as light sources, as well as glass fibers engineered to guide light waves over worthwhile distances for optical communication, WDM systems, and SONET/SDH systems     

在线暂态稳定计算程序的设计与实现

提出了一种基于COM组件技术的在线暂态稳定计算程序的设计与实现方法。着重介绍了通信模块、暂态稳定计算模块以及结果输出模块的实现方法。基于IEC61970标准设计的通信模块使得在线计算程序的“即插即用”成为可能。采用基于COM的统一接口设计以及数据结构设计,提高了程序的灵活性和可重用性。最后,简单介绍了基于分布式组件技术的暂态稳定时间并行计算的实现方法。     

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。     

输电线路对短波无线电测向台(站)无源干扰的保护间距

为解决输电线路对短波无线电测向台(站)的无源干扰问题,通过改变计算模型中参数的方法,研究了输电线路在无线电波激励下对无线电测向台的电磁干扰影响因素及影响规律。研究结果表明,计算无源干扰时,入射波方向应取0或90的最大影响方向,且铁塔阵列中的铁塔数目取30座可以满足计算精度需求。还计算了不同电压等级的输电线路对短波无线电测向台的保护间距,相比之下,国标规定的保护间距较为保守。依据文中的研究结果和以往工程中的实践经验,提出了为降低输电线路对短波无线电测向台的无源干扰,可在输电线路方面和短波无线电测向台方面采取的防护措施。