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Computational nanoelectronics is an emerging multi-disciplinary field covering condensed matter physics, applied mathematics, computer science, and electronic engineering. In recent decades, a few state-of-the-art software packages have been developed to carry out first-principle atomistic device simulations. Nevertheless those packages are either black boxes (commercial codes) or accessible only to very limited users (private research codes). The purpose of this book is to open one of the commercial black boxes, and to demonstrate the complete procedure from theoretical derivation, to numerical implementation, all the way to device simulation. Meanwhile the affiliated source code constitutes an open platform for new researchers. This is the first book of its kind. We hope the book will make a modest contribution to the field of computational nanoelectronics.
"Computational nanoelectronics is an emerging multi-disciplinary field covering condensed matter physics, applied mathematics, computer science, and electronic engineering. In recent decades, a few state-of-the-art software packages have been developed to carry out first-principle atomistic device simulations. Nevertheless those packages are either black boxes (commercial codes) or accessible only to very limited users (private research codes). The purpose of this book is to open one of the commercial black boxes, and to demonstrate the complete procedure from theoretical derivation, to numerical implementation, all the way to device simulation. Meanwhile the affiliated source code constitutes an open platform for new researchers. This is the first book of its kind. We hope the book will make a modest contribution to the field of computational nanoelectronics"--
This book surveys the advanced simulation methods needed for proper modeling of state-of-the-art nanoscale devices. It systematically describes theoretical approaches and the numerical solutions that are used in explaining the operation of both power devices as well as nano-scale devices. It clearly explains for what types of devices a particular method is suitable, which is the most critical point that a researcher faces and has to decide upon when modeling semiconductor devices.
This dissertation, "Efficiency Enhancement for Nanoelectronic Transport Simulations" by Jun, Huang, 黃俊, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Continual technology innovations make it possible to fabricate electronic devices on the order of 10nm. In this nanoscale regime, quantum physics becomes critically important, like energy quantization effects of the narrow channel and the leakage currents due to tunneling. It has also been utilized to build novel devices, such as the band-to-band tunneling field-effect transistors (FETs). Therefore, it presages accurate quantum transport simulations, which not only allow quantitative understanding of the device performances but also provide physical insight and guidelines for device optimizations. However, quantum transport simulations usually require solving repeatedly the Green's function or the wave function of the whole device region with open boundary treatment, which are computationally cumbersome. Moreover, to overcome the short-channel effects, modern devices usually employ multi-gate structures that are three-dimensional, making the computation very challenging. It is the major target of this thesis to enhance the simulation efficiency by proposing several fast numerical algorithms. The other target is to apply these algorithms to study the physics and performances of some emerging electronic devices. First, an efficient method is implemented for real space simulations with the effective mass approximation. Based on the wave function approach, asymptotic waveform evaluation combined with a complex frequency hopping algorithm is successfully adopted to characterize electron conduction over a wide energy range. Good accuracy and efficiency are demonstrated by simulating several n-type multi-gate silicon FETs. This technique is valid for arbitrary potential distribution and device geometry, making it a powerful tool for studying n-type silicon nanowire (SiNW) FETs in the presence of charged impurity and surface roughness scattering. Second, a model order reduction (MOR) method is proposed for multiband simulation of nanowire structures. Employing three- or six-band k.p Hamiltonian, the non-equilibrium Green's function (NEGF) equations are projected into a much smaller subspace constructed by sampling the Bloch modes of each cross-section layer. Together with special sampling schemes and Krylov subspace methods for solving the eigenmodes, large cross-section p-type SiNW FETs can be simulated. A novel device, junctionless FET, is then investigated. It is found that its doping density, channel orientation, and channel size need to be carefully optimized in order to outperform the classical inversion-mode FET. With a spurious band elimination process, the MOR method is subsequently extended to the eight-band k.p model, allowing simulation of band-to-band tunneling devices. In particular, tunneling FETs with indium arsenide (InAs) nanowire channel are studied, considering different channel orientations and configurations with source pockets. Results suggest that source pocket has no significant impact on the performances of the nanowire device due to its good electrostatic integrity. At last, improvements are made for open boundary treatment in atomistic simulations. The trick is to condense the Hamiltonian matrix of the periodic leads before calculating the surface Green's function. It is very useful for treating leads with long unit cells. DOI: 10.5353/th_b5153685 Subjects: Nanoelectronics - Mathematical methods
As the miniaturization of devices begins to reveal the atomic nature of materials, where chemical bonding and quantum effects are important, one must resort to a parameter-free theory for predictions. This thesis theoretically investigates the quantum transport properties of nanoelectronic devices using atomistic first principles. Our theoretical formalism employs density functional theory (DFT) in combination with Keldysh nonequilibrium Green's functions (NEGF). Self-consistently solving the DFT Hamiltonian with the NEGF charge density provides a way to simulate nonequilibrium systems without phenomenological parameters. This state-of-the-art technique was used to study three problems related to the field of nanoelectronics. First, we investigated the role of metallic contacts (Cu, Ni and Co) on the transport characteristics of graphene devices. With Cu, the graphene is simply electron-doped (Fermi level shift of -0.7 eV) which creates a unique signature in ...
The emergence of nanoelectronics has led us to renew the concepts of transport theory used in semiconductor device physics and the engineering community. It has become crucial to question the traditional semi-classical view of charge carrier transport and to adequately take into account the wave-like nature of electrons by considering not only their coherent evolution but also the out-of-equilibrium states and the scattering effects. 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.
Everyone is familiar with the amazing performance of a modern smartphone, powered by a billion-plus nanotransistors, each having an active region that is barely a few hundred atoms long. The same amazing technology has also led to a deeper understanding of the nature of current flow and heat dissipation on an atomic scale which is of broad relevance to the general problems of non-equilibrium statistical mechanics that pervade many different fields.This book is based on a set of two online courses originally offered in 2012 on nanoHUB-U and more recently in 2015 on edX. In preparing the second edition the author decided to split it into parts A and B titled Basic Concepts and Quantum Transport respectively, along the lines of the two courses. A list of available video lectures corresponding to different sections of this volume is provided upfront.To make these lectures accessible to anyone in any branch of science or engineering, the author assume very little background beyond linear algebra and differential equations. However, the author will be discussing advanced concepts that should be of interest even to specialists, who are encouraged to look at his earlier books for additional technical details.
This dissertation, "Multi-terminal Nano-electronic Device Simulations With Atomistic Details" by Siu-kong, Koo, 顧兆光, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Miniaturization of electronics is an unstoppable trend in the semiconductor industry. Moore's Law has been the driving force to the advancement of the industry for half a century; and will continue to be the indicator for technology developments. As the feature size of an electronic device is reducing to the nano-scale level, quantum mechanics and atomistic details will become more and more important. In addition, simulations on devices with two or more terminals, such as transistors or junctions, are essential for design of electronics. Thus, Quantum mechanics based method with atomistic details for simulations of nano-electronic devices with two or more terminals is proposed and demonstrated. Similar studies can be found in the literature. However, most work was focusing on static / steady state problems, only few had looked into the dynamics. On the other hand, most methods being used in previous work can only handle two-terminal devices, while those few methods which can be applied for multi-terminal devices can only deal with steady state problems. Therefore, there is a research gap lies in multi-terminal time-dependent device simulations; and this gap will be filled by the work in this thesis. Quantum mechanics based method for open system has been used to simulate the electrical response through nano-electronic devices. Nearest neighbor tight binding models and carbon based models are the systems of interests. The core part of the structures of the systems of interest is a hexagonal ring. This is essentially a benzene ring based structure in our studies. Several situations for electrodes connecting the benzene ring at para- and metapositions are considered. Two-terminal cases and three-terminal cases for the mentioned systems have been studied. The third terminal in the three-terminal case is basically being viewed as a probe to the corresponding two-terminal case. For all the cases, steady state currents have been calculated; and currentvoltage curves of the systems have been obtained. Transient currents have also been calculated, so that dynamic responses of the systems are revealed. Different magnitudes of bias voltages have been applied to the systems. Linear response of the currents through the devices with respect to the bias voltage is observed for most cases. The para-position case can be taken as a reference to the meta-position case, due to simple structure and well-behaved responses. Interesting electric responses from the meta-position case is observed. The possibility for the meta-position system to be used as a transistor or other devices is briefly discussed. DOI: 10.5353/th_b5312347 Subjects: Nanoelectromechanical systems
Les effets de surface peuvent affecter la performance d'un dispositif nanoélectronique, mais peuvent aussi conduire à de nouvelles fonctionnalités. L'objectif de cette thèse est d'effectuer une étude théorique sur le rôle des surfaces en nanoélectronique. Notre analyse, de type premiers principes atomiques, est effectuée en combinant la théorie de la fonctionnelle de la densité avec les fonctions de Green hors-équilibre. Cette technique permet de traiter tous les atomes de manière égale sans utiliser de paramètres phénoménologiques. La première partie de cette thèse considère la conduction à travers une molécule sans substrat, afin d'illustrer le genre de systèmes typiquement modélisés dans les calculs de transport. Deux électrodes en Au sont mises en contactavec une molécule benzènediamine substituée (R = CH3, NH2, OH), où un atome H est retiré pour former un radical qui peut se comporter comme un filtre de spin, dépendant du ...