Search results for: transport-simulation-in-nanodevices

Transport Simulation in Nanodevices

Author : Philippe Dollfus
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Linear current-voltage pattern, has been and continues to be the basis for characterizing, evaluating performance, and designing integrated circuits, but is shown not to hold its supremacy as channel lengths are being scaled down. In a nanoscale circuit with reduced dimensionality in one or more of the three Cartesian directions, quantum effects transform the carrier statistics. In the high electric field, the collision free ballistic transform is predicted, while in low electric field the transport remains predominantly scattering-limited. In a micro/nano-circuit, even a low logic voltage of 1 V is above the critical voltage triggering nonohmic behavior that results in ballistic current saturation. A quantum emission may lower this ballistic velocity.

Simulation of Transport in Nanodevices

Author : François Triozon
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Simulation of Transport in Nanodevices

Author : François Triozon
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Linear current-voltage pattern, has been and continues to be the basis for characterizing, evaluating performance, and designing integrated circuits, but is shown not to hold its supremacy as channel lengths are being scaled down. In a nanoscale circuit with reduced dimensionality in one or more of the three Cartesian directions, quantum effects transform the carrier statistics. In the high electric field, the collision free ballistic transform is predicted, while in low electric field the transport remains predominantly scattering-limited. In a micro/nano-circuit, even a low logic voltage of 1 V is above the critical voltage triggering nonohmic behavior that results in ballistic current saturation. A quantum emission may lower this ballistic velocity.

Simulation of Transport in Nanodevices

Author : Fran?ois Triozon
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Linear current-voltage pattern, has been and continues to be the basis for characterizing, evaluating performance, and designing integrated circuits, but is shown not to hold its supremacy as channel lengths are being scaled down. In a nanoscale circuit with reduced dimensionality in one or more of the three Cartesian directions, quantum effects transform the carrier statistics. In the high electric field, the collision free ballistic transform is predicted, while in low electric field the transport remains predominantly scattering-limited. In a micro/nano-circuit, even a low logic voltage of 1 V is above the critical voltage triggering nonohmic behavior that results in ballistic current saturation. A quantum emission may lower this ballistic velocity.

Reduced Basis Method for Nanodevices Simulation

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Ballistic transport simulation in nanodevices, which involves self-consistently solving a coupled Schrodinger-Poisson system of equations, is usually computationally intensive. Here, we propose coupling the reduced basis method with the subband decomposition method to improve the overall efficiency of the simulation. By exploiting a posteriori error estimation procedure and greedy sampling algorithm, we are able to design an algorithm where the computational cost is reduced significantly. In addition, the computational cost only grows marginally with the number of grid points in the confined direction.

Physics and Modeling of Tera and Nano devices

Author : Maxim Ryzhii
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Physics and Modeling of Tera- and Nano-Devices is a compilation of papers by well-respected researchers working in the field of physics and modeling of novel electronic and optoelectronic devices. The topics covered include devices based on carbon nanotubes, generation and detection of terahertz radiation in semiconductor structures including terahertz plasma oscillations and instabilities, terahertz photomixing in semiconductor heterostructures, spin and microwave-induced phenomena in low-dimensional systems, and various computational aspects of device modeling. Researchers as well as graduate and postgraduate students working in this field will benefit from reading this book. Sample Chapter(s). Semiconductor Device Scaling: Physics, Transport, and the Role of Nanowires (784 KB). Contents: Semiconductor Device Scaling: Physics, Transport, and the Role of Nanowires (D K Ferry et al.); Polaronic Effects at the Field Effect Junctions for Unconventional Semiconductors (N Kirova); Cellular Monte Carlo Simulation of High Field Transport in Semiconductor Devices (S M Goodnick & M Saraniti); Nanoelectronic Device Simulation Based on the Wigner Function Formalism (H Kosina); Quantum Simulations of Dual Gate MOSFET Devices: Building and Deploying Community Nanotechnology Software Tools on nanoHUB.org (S Ahmed et al.); Positive Magneto-Resistance in a Point Contact: Possible Manifestation of Interactions (V T Renard et al.); Impact of Intrinsic Parameter Fluctuations in Nano-CMOS Devices on Circuits and Systems (S Roy et al.); HEMT-Based Nanometer Devices Toward Terahertz Era (E Sano & T Otsuji); Plasma Waves in Two-Dimensional Electron Systems and Their Applications (V Ryzhii et al.); Resonant Terahertz Detection Antenna Utilizing Plasma Oscillations in Lateral Schottky Diode (A Satou et al.); Terahertz Polarization Controller Based on Electronic Dispersion Control of 2D Plasmons (T Nishimura & T Otsuji); Higher-Order Plasmon Resonances in GaN-Based Field-Effect Transistor Arrays (V V Popov et al.); Ultra-Highly Sensitive Terahertz Detection Using Carbon-Nanotube Quantum Dots (Y Kawano et al.); Generation of Ultrashort Electron Bunches in Nanostructures by Femtosecond Laser Pulses (A Gladun et al.); Characterization of Voltage-Controlled Oscillator Using RTD Transmission Line (K Narahara et al.); Infrared Quantum-Dot Detectors with Diffusion-Limited Capture (N Vagidov et al.); Magnetoresistance in Fe/MgO/Fe Magentic Tunnel Junctions (N N Beleskii et al.); Modeling and Implementation of Spin-Based Quantum Computation (M E Hawley et al.); Quantum Engineering for Threat Reduction and Homeland Security (G P Berman et al.); Strong Phase Shift Mask Manufacturing Error Impact on the 65nm Poly Line Printability (N Belova). Readership: Academics, graduate and postgraduate students in the field of physics and modeling of novel electronics and optoelectronic devices.

A Nested Dissection Approach to Modeling Transport in Nanodevices

Author : Yunqi Zhao
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Modeling nanoscale devices quantum mechanically is a computationally challenging problem where new methods to solve the underlying equations are in a dire need. In this Ph.D. work, we design and implement an efficient and high quality numerical algorithm to solve Green's functions, within the framework of non-equilibrium Green's function (NEGF) calculation, which is the most accurate approach in electronic transport simulation. Our approach exploits and extends a recent advance in using an established graph partitioning method, namely the nested dissection. The developed method has the capability to handle open boundary conditions that are represented by full self-energy matrices required for realistic modeling of nanoscale devices. We demonstrate that our method has a reduced complexity and significant speedup compared to the state-of-the-art recursive Green's function (RGF) approach across a variety of two-dimensional systems and, more important, three-dimensional structures including the traditional silicon nanowire, emerging graphene based multilayer devices, and DNA molecules. As a novel application of the proposed simulator, we investigate the tunneling transport properties of heterostructures consisting of a few atomic layers thick hexagonal Boron Nitride (hBN) film sandwiched between armchair edged graphene nanoribbon electrodes. By incorporating our efficient Green's function solver, the modeled device ranges from a small system with 6,000 atoms to experimental feasible sizes up to 70,000 atoms. We show a gate-controllable vertical transistor exhibiting strong negative differential resistance (NDR) effect with multiple resonant peaks, which originate from two distinct mechanisms depending on the gate and applied bias in the same device. We perform a scaling analysis of the NDR feature as a function of the system size and gain instructive insights for future theoretical and experimental investigations. To convey more experimentally realistic simulation, we incorporate (i) angular misorientation between multilayer heterostructure, which inducing a distinct resonant mechanism depending on both gate bias and twisting angle; (ii) electron-phonon scattering decoherence mechanism, which successfully captures the current NDR peaks degradation observed in room-temperature experiments. The NDR feature with multiple resonant peaks, combined with the ultrafast tunneling speed provides prospect for the graphene-hBN-graphene heterostructure in the high-performance electronics.

Theory and Simulation Methods for Electronic and Phononic Transport in Thermoelectric Materials

Author : Neophytos Neophytou
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This book introduces readers to state-of-the-art theoretical and simulation techniques for determining transport in complex band structure materials and nanostructured-geometry materials, linking the techniques developed by the electronic transport community to the materials science community. Starting from the semi-classical Boltzmann Transport Equation method for complex band structure materials, then moving on to Monte Carlo and fully quantum mechanical models for nanostructured materials, the book addresses the theory and computational complexities of each method, as well as their advantages and capabilities. Presented in language that is accessible to junior computational scientists, while including enough detail and depth with regards to numerical implementation to tackle modern research problems, it offers a valuable resource for computational scientists and postgraduate researchers whose work involves the theory and simulation of electro-thermal transport in advanced materials.

Nanostructures

Author : Christophe Jean Delerue
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Provides the theoretical background needed by physicists, engineers and students to simulate nano-devices, semiconductor quantum dots and molecular devices. It presents in a unified way the theoretical concepts, the more recent semi-empirical and ab initio methods, and their application to experiments. The topics include quantum confinement, dielectric and optical properties, non-radiative processes, defects and impurities, and quantum transport. This guidebook not only provides newcomers with an accessible overview (requiring only basic knowledge of quantum mechanics and solid-state physics) but also provides active researchers with practical simulation tools.

Transport of Information Carriers in Semiconductors and Nanodevices

Author : El-Saba, Muhammad
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Rapid developments in technology have led to enhanced electronic systems and applications. When utilized correctly, these can have significant impacts on communication and computer systems. Transport of Information-Carriers in Semiconductors and Nanodevices is an innovative source of academic material on transport modelling in semiconductor material and nanoscale devices. Including a range of perspectives on relevant topics such as charge carriers, semiclassical transport theory, and organic semiconductors, this is an ideal publication for engineers, researchers, academics, professionals, and practitioners interested in emerging developments on transport equations that govern information carriers.

Schr dinger Equation Monte Carlo Simulation of Nanoscale Devices

Author : Xin Zheng
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Some semiconductor devices such as lasers have long had critical dimensions on the nanoscale where quantum effects are critical. Others such as MOSFETs are now being scaled to within this regime. Quantum effects neglected in semiclassical models become increasing important at the nanoscale. Meanwhile, scattering remains important even in MOSFETs of 10 nm and below. Therefore, accurate quantum transport simulators with scattering are needed to explore the essential device physics at the nanoscale. The work of this dissertation is aimed at developing accurate quantum transport simulation tools for deep submicron device modeling, as well as utilizing these simulation tools to study the quantum transport and scattering effects in the nano-scale semiconductor devices. The basic quantum transport method "Schrödinger Equation Monte Carlo" (SEMC) provides a physically rigorous treatment of quantum transport and phasebreaking inelastic scattering (in 3D) via real (actual) scattering processes such as optical and acoustic phonon scattering. The SEMC method has been used previously to simulate carrier transport in nano-scaled devices in order to gauge the potential reliability of semiclassical models, phase-coherent quantum transport, and other limiting models as the transition from classical to quantum transport is approached. In this work, SEMC-1D and SEMC-2D versions with long range polar optical scattering processes have been developed and used to simulate quantum transport in tunnel injection lasers and nanoscaled III-V MOSFETs. Simulation results serve not only to demonstrate the capabilities of the developed quantum transport simulators, but also to illuminate the importance of physically accurate simulation of scattering for the predictive modeling of transport in nano-scaled devices.

Quantum Transport in Nanodevices

Author : Brandon Girard Cook
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Nanostructures

Author : Christophe Jean Delerue
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Finite Element Modeling and Simulation of Photoconductive and Ballistic Semiconductor Nanodevices

Author : Gregg Guarino
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"This thesis presents models, simulation techniques, and simulation results for two types of semiconductor nanodevice; the metal-semiconductor-metal (MSM) photodetector, and the ballistic deflection transistor (BDT). Our simulation tools were developed using the commercial Comsol[trademark symbol] finite element analysis (FEA) field solver to obtain the numeric solutions. Finite element models have been developed for both an alloyed- and surface-contact MSM photodetector. The simulation results agree with previously reported experimental data. The alloyed device, despite having a somewhat larger capacitance, has a non-illuminated region of lower resistance with a more-uniform and deeper-penetrating electric field and carrier transport current. The latter explains, in terms of the equivalent lumped parameters, the experimentally observed faster response of such device. The model was further used to predict improved responsivity, based on electrode spacing and antireflective coating, as well as the optimal depth of the alloyed contact being approximately half of the optical penetration depth. For the BDT, novel simulation techniques, also based on the FEA method, have been developed. The results demonstrate that diffusive transport is capable of predicting the current vs. voltage characteristics of the current-generation of BDTs, as well as the effects of selected changes in the BDT geometry. Simulation results were used to predict the characteristics of several variations of scaled-down and geometry-modified devices and other physical parameters. Also, the newly introduced concept of ballistic conductivity predicts behavior consistent with ballistic transport, relative to the effect of the deflector, for small devices."--Leaves vii-viii.

Physics and Modeling of Tera and Nano Devices

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Computational Investigations of Molecular Transport Processes in Nanotubular and Nanocomposite Materials

Author : Suchitra Konduri
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The unique physical properties of nanomaterials, attributed to the combined effects of their size, shape, and composition, have sparked significant interest in the field of nanotechnology. Fabrication of nanodevices using nanomaterials as building-blocks are underway to enable novel technological applications. A fundamental understanding on the structure-property relationships and the mechanism of synthesizing nanomaterials with tailored physical properties is critical for a rationale design of functional nanodevices. In this thesis, molecular simulations that employ a detailed atomistic description of the nanoscopic structures were used to understand the structure-transport property relationships in two novel classes of porous nanomaterials, namely, polymer/porous inorganic layered nanocomposite materials and single-walled metal oxide nanotubes, and provide predictions for the design of nanodevices using these nanomaterials.

Nanotechnology Research Directions IWGN Workshop Report

Author : Iwgn Workshop (1999)
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This book documents recent dramatic breakthroughs and prospects for even more important future developments in a wide variety of fields and applications of science and technology related to `nanotechnology', all involving the control of matter on the nanometer-length scale, that is, at the level of atoms, molecules, and supramolecular structures. As the twenty-first century unfolds, nanotechnology's impact on the health, wealth, and security of the world's people is expected to be at least as significant as the combined influences in this century of antibiotics, the integrated circuit, and human-made polymers. The book covers fundamental scientific issues for nanotechnology and reviews progress in the development of the necessary tools for nanotechnology research and applications (e.g. theory, modeling and simulation, experimental methods, and instruments such as scanning probe microscopes). It also surveys a wide variety of current and potential application areas of nanotechnology, including: dispersions, coatings, and large surface area structures; nanodevices, nanoelectronics, and nanosensors; materials science and applications of bulk nanostructured materials with novel properties; biology, medicine, and healthcare; and energy, chemicals, and environmental science. The book incorporates the views of leading experts from U.S. government, academia, and the private sector. It reflects the consensus reached at a workshop held in January 1999, and detailed in contributions submitted thereafter by members of the U.S. science and engineering community. It describes challenges that are posed and opportunities that are offered by nanotechnology and outlines the steps that must be taken in order for humanity to benefit from the advances that are envisioned. This emphasizes three crucial areas: developing a balanced research and development infrastructure, advancing critical research areas, and nurturing the scientific and technical workforce of the next century.

The Wigner Monte Carlo Method for Nanoelectronic Devices

Author : Damien Querlioz
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This book gives an overview of the quantum transport approaches for nanodevices and focuses on the Wigner formalism. It details the implementation of a particle-based Monte Carlo solution of the Wigner transport equation and how the technique is applied to typical devices exhibiting quantum phenomena, such as the resonant tunnelling diode, the ultra-short silicon MOSFET and the carbon nanotube transistor. In the final part, decoherence theory is used to explain the emergence of the semi-classical transport in nanodevices.

Beyond CMOS Nanodevices 2

Author : Francis Balestra
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This book offers a comprehensive review of the state-of-the-art in innovative Beyond-CMOS nanodevices for developing novel functionalities, logic and memories dedicated to researchers, engineers and students. The book will particularly focus on the interest of nanostructures and nanodevices (nanowires, small slope switches, 2D layers, nanostructured materials, etc.) for advanced More than Moore (RF-nanosensors-energy harvesters, on-chip electronic cooling, etc.) and Beyond-CMOS logic and memories applications.

Quantum and Classical Simulation of Electronic Transport at the Nanoscale

Author : Daniel S. Gruss
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Time-dependent electronic transport is increasingly important to the state-of-the-art device design and fabrication. The development of nanoscale sensing, the harnessing and control of structural fluctuations, and the advancement of next-generation materials all require a treatment of quantum dynamics beyond the level of traditional methods and a more nuanced approach to the quantum/classical divide. It is thus becoming necessary to incorporate new theoretical approaches--as well as efficient computational tools--to fully understand the underlying physical processes in these systems, as well as the approximations used to solve for their behavior. In addition, recent progress in ultra-cold atom experiments allows for the direct observation of many-body transport in the laboratory--a form of quantum simulation--which provides a parallel technique for solving these problems. We focus on simulation methods for electronic dynamics, from cold-atom to computational approaches. To this end, we examine the use of atomic transport in elucidating the nature of electronic transport and the simulation of the latter in classical computers. In particular, we develop an analog of a scanning tunneling microscope and a corresponding operational meaning of the local density of states for strongly interacting particles--a situation where the concept of quasi-particles cannot often be used. This technique captures the energetic structure of a many-body system through the measurement of particle transport, as well as gives a novel approach to numerically characterize the system. We also demonstrate how interactions can generate steady-state currents in fermionic cold-atom systems, as opposed to globally biased systems. We then shift our attention to the extension of numerical simulations of quantum transport to an open-system formalism--that is, inclusion of an external environment that drives the system out of equilibrium. We include an explicit treatment of the electronic reservoirs of a device with a corresponding finite-time relaxation. This yields a computationally efficient method for simulation of dynamics under non-equilibrium conditions. Moreover, it gives a general simulation technique for finding periodic steady-states, the decay of local disturbances, and the real-time response to structural changes.