The operation of semiconductor devices depends upon the use of electrical potential barriers (such as gate depletion) in controlling the carrier densities (electrons and holes) and their transport. Although a successful device design is quite complicated and involves many aspects, the device engineering is mostly to devise a "best" device design by defIning optimal device structures and manipulating impurity profIles to obtain optimal control of the carrier flow through the device. This becomes increasingly diffIcult as the device scale becomes smaller and smaller. Since the introduction of integrated circuits, the number of individual transistors on a single chip has doubled approximately every three years. As the number of devices has grown, the critical dimension of the smallest feature, such as a gate length (which is related to the transport length defIning the channel), has consequently declined. The reduction of this design rule proceeds approximately by a factor of 1. 4 each generation, which means we will be using 0. 1-0. 15 ). lm rules for the 4 Gb chips a decade from now. If we continue this extrapolation, current technology will require 30 nm design rules, and a cell 3 2 size < 10 nm , for a 1Tb memory chip by the year 2020. New problems keep hindering the high-performance requirement. Well-known, but older, problems include hot carrier effects, short-channel effects, etc. A potential problem, which illustrates the need for quantum transport, is caused by impurity fluctuations.

1. An Introductory Review.- 2. Fabrication Techniques for Submicron Devices.- 3. Heterojunctions and Interfaces.- 4. Semiclassical Carrier Transport Models.- 5. Transient Hot-Carrier Transport.- 6. Alloys and Superlattices.- 7. The Electron-Electron Interaction.- 8. Lateral Surface Superlattices.- 9. Quantum Transport in Small Structures.- 10. Noise in Submicron Devices.

The papers contained in the volume represent lectures delivered as a 1983 NATO ASI, held at Urbino, Italy. The lecture series was designed to identify the key submicron and ultrasubmicron device physics, transport, materials and contact issues. Nonequilibrium transport, quantum transport, interfacial and size constraints issues were also highlighted. The ASI was supported by NATO and the European Research Office. H. L. Grubin D. K. Ferry C. Jacoboni v CONTENTS MODELLING OF SUB-MICRON DEVICES.................. .......... 1 E. Constant BOLTZMANN TRANSPORT EQUATION... ... ...... .................... 33 K. Hess TRANSPORT AND MATERIAL CONSIDERATIONS FOR SUBMICRON DEVICES. . .. . . . . .. . . . .. . .. . .... ... .. . . . .. . . . .. . . . . . . . . . . 45 H. L. Grubin EPITAXIAL GROWTH FOR SUB MICRON STRUCTURES.................. 179 C. E. C. Wood INSULATOR/SEMICONDUCTOR INTERFACES.......................... 195 C. W. Wilms en THEORY OF THE ELECTRONIC STRUCTURE OF SEMICONDUCTOR SURFACES AND INTERFACES......................................... 223 C. Calandra DEEP LEVELS AT COMPOUND-SEMICONDUCTOR INTERFACES........... 253 W. Monch ENSEMBLE MONTE CARLO TECHNIqUES............................. 289 C. Jacoboni NOISE AND DIFFUSION IN SUBMICRON STRUCTURES................. 323 L. Reggiani SUPERLATTICES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361 . . . . . . . . . . . . K. Hess SUBMICRON LITHOGRAPHY 373 C. D. W. Wilkinson and S. P. Beaumont QUANTUM EFFECTS IN DEVICE STRUCTURES DUE TO SUBMICRON CONFINEMENT IN ONE DIMENSION.... ....................... 401 B. D. McCombe vii viii CONTENTS PHYSICS OF HETEROSTRUCTURES AND HETEROSTRUCTURE DEVICES..... 445 P. J. Price CORRELATION EFFECTS IN SHORT TIME, NONS TAT I ONARY TRANSPORT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477 . . . . . . . . . . . . J. J. Niez DEVICE-DEVICE INTERACTIONS............ ...................... 503 D. K. Ferry QUANTUM TRANSPORT AND THE WIGNER FUNCTION................... 521 G. J. Iafrate FAR INFRARED MEASUREMENTS OF VELOCITY OVERSHOOT AND HOT ELECTRON DYNAMICS IN SEMICONDUCTOR DEVICES............. 577 S. J. Allen, Jr.

The technological means now exists for approaching the fundamentallimiting scales of solid state electronics in which a single carrier can, in principle, represent a single bit in an information flow. In this light, the prospect of chemically, or biologically, engineered molccular-scale structures which might support information processing functions has enticed workers for many years. The one common factor in all suggested molecular switches, ranging from the experimentally feasible proton-tunneling structure, to natural systems such as the micro-tubule, is that each proposed structure deals with individual information carrying entities. Whereas this future molecular electronics faces enormous technical challenges, the same Iimit is already appearing in existing semiconducting quantum wires and small tunneling structures, both superconducting and normal meta! devices, in which the motion of a single eh arge through the tunneling barrier can produce a sufficient voltage change to cut-off further tunneling current. We may compare the above situation with today's Si microelectronics, where each bit is encoded as a very !arge number, not necessarily fixed, of electrons within acharge pulse. The associated reservoirs and sinks of charge carriers may be profitably tapped and manipulated to proviele macro-currents which can be readily amplified or curtailed. On the other band, modern semiconductor ULSI has progressed by adopting a linear scaling principle to the down-sizing of individual semiconductor devices.

As we settle into this second decade of the 21st century it is evident that the advances in microelectronics have truly revolutionized our day-to-day lifestyle. The growth of microelectronics itself has been driven, and in turn is calibrated by, the growth in density of transistors on a single integrated circuit, a growth that has come to be known as Moore's Law. Considering that the first transistor appeared only at the middle of the last century, it is remarkable that billions of transistors can now appear on a single chip. The technology is built upon semiconductors, materials in which the band gap has been engineered for special values suitable to the particular application. This book, written specifically for a one-semester course for graduate students, provides a thorough understanding of the key solid-state physics of semiconductors and prepares readers for further advanced study, research and development work in semiconductor materials and applications. The book describes how quantum mechanics gives semiconductors unique properties that enabled the microelectronics revolution, and sustain the ever-growing importance of this revolution. Including chapters on electronic structure, lattice dynamics, electron-phonon interactions and carrier transport it also discusses theoretical methods for computation of band structure, phonon spectra, the electron-phonon interaction and transport of carriers.

The majority of the chapters in this volume represent a series of lectures. that were given at a workshop on quantum transport in ultrasmall electron devices, held at San Miniato, Italy, in March 1987. These have, of course, been extended and updated during the period that has elapsed since the workshop was held, and have been supplemented with additional chapters devoted to the tunneling process in semiconductor quantum-well structures. The aim of this work is to review and present the current understanding in nonequilibrium quantum transport appropriate to semiconductors. Gen erally, the field of interest can be categorized as that appropriate to inhomogeneous transport in strong applied fields. These fields are most likely to be strongly varying in both space and time. Most of the literature on quantum transport in semiconductors (or in metallic systems, for that matter) is restricted to the equilibrium approach, in which spectral densities are maintained as semiclassical energy conserving delta functions, or perhaps incorporating some form of collision broadening through a Lorentzian shape, and the distribution functions are kept in the equilibrium Fermi-Dirac form. The most familiar field of nonequilibrium transport, at least for the semiconductor world, is that of hot carriers in semiconductors."

Throughout their college career, most engineering students have done problems and studies that are basically situated in the classical world. Some may have taken quantum mechanics as their chosen field of study. This book moves beyond the basics to highlight the full quantum mechanical nature of the transport of carriers through nanoelectronic structures. The book is unique in that addresses quantum transport only in the materials that are of interest to microelectronics-semiconductors, with their variable densities and effective masses. The author develops Green's functions starting from equilibrium Green's functions and going through modern time-dependent approaches to non-equilibrium Green's functions, introduces relativistic bands for graphene and topological insulators and discusses the quantum transport changes that these bands induce, and discusses applications such as weak localization and phase breaking processes, resonant tunneling diodes, single-electron tunneling, and entanglement. Furthermore, he also explains modern ensemble Monte Carlo approaches to simulation of various approaches to quantum transport and the hydrodynamic approaches to quantum transport. All in all, the book describes all approaches to quantum transport in semiconductors, thus becoming an essential textbook for advanced graduate students in electrical engineering or physics.

Modern electronics is being transformed as device size decreases to a size where the dimensions are significantly smaller than the constituent electron's mean free path. In such systems the electron motion is strongly confined resulting in dramatic changes of behaviour compared to the bulk. This book introduces the physics and applications of transport in such mesoscopic and nanoscale electronic systems and devices. The behaviour of these novel devices is influenced by numerous effects not seen in bulk semiconductors, such as the Aharonov-Bohm Effect, disorder and localization, energy quantization, electron wave interference, spin splitting, tunnelling and the quantum hall effect to name a few. Including coverage of recent developments, and with a chapter on carbon-based nanoelectronics, this book will provide a good course text for advanced students or as a handy reference for researchers or those entering this interdisciplinary area.

Is Bigger Always Better? Explore the Behavior of Very Small Devices as Described by Quantum Mechanics Smaller is better when it comes to the semiconductor transistor. Nanoscale Silicon Devices examines the growth of semiconductor device miniaturization and related advances in material, device, circuit, and system design, and highlights the use of device scaling within the semiconductor industry. Device scaling, the practice of continuously scaling down the size of metal-oxide-semiconductor field-effect transistors (MOSFETs), has significantly improved the performance of small computers, mobile phones, and similar devices. The practice has resulted in smaller delay time and higher device density in a chip without an increase in power consumption. This book covers recent advancements and considers the future prospects of nanoscale silicon (Si) devices. It provides an introduction to new concepts (including variability in scaled MOSFETs, thermal effects, spintronics-based nonvolatile computing systems, spin-based qubits, magnetoelectric devices, NEMS devices, tunnel FETs, dopant engineering, and single-electron transfer), new materials (such as high-k dielectrics and germanium), and new device structures in three dimensions. It covers the fundamentals of such devices, describes the physics and modeling of these devices, and advocates further device scaling and minimization of energy consumption in future large-scale integrated circuits (VLSI). Additional coverage includes: Physics of nm scaled devices in terms of quantum mechanics Advanced 3D transistors: tri-gate structure and thermal effects Variability in scaled MOSFET Spintronics on Si platform NEMS devices for switching, memory, and sensor applications The concept of ballistic transport The present status of the transistor variability and more An indispensable resource, Nanoscale Silicon Devices serves device engineers and academic researchers (including graduate students) in the fields of electron devices, solid-state physics, and nanotechnology.

The technological means now exists for approaching the fundamentallimiting scales of solid state electronics in which a single carrier can, in principle, represent a single bit in an information flow. In this light, the prospect of chemically, or biologically, engineered molccular-scale structures which might support information processing functions has enticed workers for many years. The one common factor in all suggested molecular switches, ranging from the experimentally feasible proton-tunneling structure, to natural systems such as the micro-tubule, is that each proposed structure deals with individual information carrying entities. Whereas this future molecular electronics faces enormous technical challenges, the same Iimit is already appearing in existing semiconducting quantum wires and small tunneling structures, both superconducting and normal meta! devices, in which the motion of a single eh arge through the tunneling barrier can produce a sufficient voltage change to cut-off further tunneling current. We may compare the above situation with today's Si microelectronics, where each bit is encoded as a very !arge number, not necessarily fixed, of electrons within acharge pulse. The associated reservoirs and sinks of charge carriers may be profitably tapped and manipulated to proviele macro-currents which can be readily amplified or curtailed. On the other band, modern semiconductor ULSI has progressed by adopting a linear scaling principle to the down-sizing of individual semiconductor devices.

The papers contained in the volume represent lectures delivered as a 1983 NATO ASI, held at Urbino, Italy. The lecture series was designed to identify the key submicron and ultrasubmicron device physics, transport, materials and contact issues. Nonequilibrium transport, quantum transport, interfacial and size constraints issues were also highlighted. The ASI was supported by NATO and the European Research Office. H. L. Grubin D. K. Ferry C. Jacoboni v CONTENTS MODELLING OF SUB-MICRON DEVICES.................. .......... 1 E. Constant BOLTZMANN TRANSPORT EQUATION... ... ...... .................... 33 K. Hess TRANSPORT AND MATERIAL CONSIDERATIONS FOR SUBMICRON DEVICES. . .. . . . . .. . . . .. . .. . .... ... .. . . . .. . . . .. . . . . . . . . . . 45 H. L. Grubin EPITAXIAL GROWTH FOR SUB MICRON STRUCTURES.................. 179 C. E. C. Wood INSULATOR/SEMICONDUCTOR INTERFACES.......................... 195 C. W. Wilms en THEORY OF THE ELECTRONIC STRUCTURE OF SEMICONDUCTOR SURFACES AND INTERFACES......................................... 223 C. Calandra DEEP LEVELS AT COMPOUND-SEMICONDUCTOR INTERFACES........... 253 W. Monch ENSEMBLE MONTE CARLO TECHNIqUES............................. 289 C. Jacoboni NOISE AND DIFFUSION IN SUBMICRON STRUCTURES................. 323 L. Reggiani SUPERLATTICES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361 . . . . . . . . . . . . K. Hess SUBMICRON LITHOGRAPHY 373 C. D. W. Wilkinson and S. P. Beaumont QUANTUM EFFECTS IN DEVICE STRUCTURES DUE TO SUBMICRON CONFINEMENT IN ONE DIMENSION.... ....................... 401 B. D. McCombe vii viii CONTENTS PHYSICS OF HETEROSTRUCTURES AND HETEROSTRUCTURE DEVICES..... 445 P. J. Price CORRELATION EFFECTS IN SHORT TIME, NONS TAT I ONARY TRANSPORT. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 477 . . . . . . . . . . . . J. J. Niez DEVICE-DEVICE INTERACTIONS............ ...................... 503 D. K. Ferry QUANTUM TRANSPORT AND THE WIGNER FUNCTION................... 521 G. J. Iafrate FAR INFRARED MEASUREMENTS OF VELOCITY OVERSHOOT AND HOT ELECTRON DYNAMICS IN SEMICONDUCTOR DEVICES............. 577 S. J. Allen, Jr.

The area of high field transport in semiconductors has been of interest since the early studies of dielectric breakdown in various materials. It really emerged as a sub-discipline of semiconductor physics in the early 1960's, following the discovery of substantial deviations from Ohm's law at high electric fields. Since that time, it has become a major area of importance in solid state electronics as semiconductor devices have operated at higher frequencies and higher powers. It has become apparent since the Modena Conference on Hot Electrons in 1973, that the area of hot electrons has ex tended weIl beyond the concept of semi-classical electrons (or holes) in homogeneous semiconductor materials. This was exemplified by the broad range of papers presented at the International Conference on Hot Electrons in Semiconductors, held in Denton, Texas, in 1977. Hot electron physics has progressed from a limited phenomeno logical science to a full-fledged experimental and precision theo retical science. The conceptual base and subsequent applications have been widened and underpinned by the development of ab initio nonlinear quantum transport theory which complements and identifies the limitations of the traditional semi-classical Boltzmann-Bloch picture. Such diverse areas as large polarons, pico-second laser excitation, quantum magneto-transport, sub-three dimensional systems, and of course device dynamics all have been shown to be strongly interactive with more classical hot electron pictures."

The purposes of this book are many. First, we must point out that it is not a device book, as a proper treatment of the range of important devices would require a much larger volume even without treating the important physics for submicron devices. Rather, the book is written principally to pull together and present in a single place, and in a (hopefully) uniform treatment, much of the understanding on relevant physics for submicron devices. Indeed, the understand ing that we are trying to convey through this work has existed in the literature for quite some time, but has not been brought to the full attention of those whose business is the making of submicron devices. It should be remarked that much of the important physics that is discussed here may not be found readily in devices at the 1.0-JLm level, but will be found to be dominant at the O.I-JLm level. The range between these two is rapidly being covered as technology moves from the 256K RAM to the 16M RAM chips."

The operation of semiconductor devices depends upon the use of electrical potential barriers (such as gate depletion) in controlling the carrier densities (electrons and holes) and their transport. Although a successful device design is quite complicated and involves many aspects, the device engineering is mostly to devise a "best" device design by defIning optimal device structures and manipulating impurity profIles to obtain optimal control of the carrier flow through the device. This becomes increasingly diffIcult as the device scale becomes smaller and smaller. Since the introduction of integrated circuits, the number of individual transistors on a single chip has doubled approximately every three years. As the number of devices has grown, the critical dimension of the smallest feature, such as a gate length (which is related to the transport length defIning the channel), has consequently declined. The reduction of this design rule proceeds approximately by a factor of 1. 4 each generation, which means we will be using 0. 1-0. 15 ). lm rules for the 4 Gb chips a decade from now. If we continue this extrapolation, current technology will require 30 nm design rules, and a cell 3 2 size < 10 nm , for a 1Tb memory chip by the year 2020. New problems keep hindering the high-performance requirement. Well-known, but older, problems include hot carrier effects, short-channel effects, etc. A potential problem, which illustrates the need for quantum transport, is caused by impurity fluctuations.

The advent of semiconductor structures whose characteristic dimensions are smaller than the mean free path of carriers has led to the development of novel devices, and advances in theoretical understanding of mesoscopic systems or nanostructures. This book has been thoroughly revised and provides a much-needed update on the very latest experimental research into mesoscopic devices and develops a detailed theoretical framework for understanding their behaviour. Beginning with the key observable phenomena in nanostructures, the authors describe quantum confined systems, transmission in nanostructures, quantum dots, and single electron phenomena. Separate chapters are devoted to interference in diffusive transport, temperature decay of fluctuations, and non-equilibrium transport and nanodevices. Throughout the book, the authors interweave experimental results with the appropriate theoretical formalism. The book will be of great interest to graduate students taking courses in mesoscopic physics or nanoelectronics, and researchers working on semiconductor nanostructures.

Is Bigger Always Better? Explore the Behavior of Very Small Devices as Described by Quantum Mechanics Smaller is better when it comes to the semiconductor transistor. Nanoscale Silicon Devices examines the growth of semiconductor device miniaturization and related advances in material, device, circuit, and system design, and highlights the use of device scaling within the semiconductor industry. Device scaling, the practice of continuously scaling down the size of metal-oxide-semiconductor field-effect transistors (MOSFETs), has significantly improved the performance of small computers, mobile phones, and similar devices. The practice has resulted in smaller delay time and higher device density in a chip without an increase in power consumption. This book covers recent advancements and considers the future prospects of nanoscale silicon (Si) devices. It provides an introduction to new concepts (including variability in scaled MOSFETs, thermal effects, spintronics-based nonvolatile computing systems, spin-based qubits, magnetoelectric devices, NEMS devices, tunnel FETs, dopant engineering, and single-electron transfer), new materials (such as high-k dielectrics and germanium), and new device structures in three dimensions. It covers the fundamentals of such devices, describes the physics and modeling of these devices, and advocates further device scaling and minimization of energy consumption in future large-scale integrated circuits (VLSI). Additional coverage includes: Physics of nm scaled devices in terms of quantum mechanics Advanced 3D transistors: tri-gate structure and thermal effects Variability in scaled MOSFET Spintronics on Si platform NEMS devices for switching, memory, and sensor applications The concept of ballistic transport The present status of the transistor variability and more An indispensable resource, Nanoscale Silicon Devices serves device engineers and academic researchers (including graduate students) in the fields of electron devices, solid-state physics, and nanotechnology.

This book was derived from a talk that the author gave at the International Conference on Advanced Nanodevices and Nanotechnology in Hawaii. The book is about science and engineering, but is not on science and engineering. It is not a textbook which develops the understanding of a small part of the field, but a book about random encounters and about the strengths and the foibles of living as a physicist and engineer for half a century. It presents the author's personal views on science, engineering, and life and is illustrated by a number of lively stories about various events, some of which shaped his life.