Field Effect Transistors, A Comprehensive Overview: From Basic Concepts to Novel Technologies

This book discusses modern-day Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) and future trends of transistor devices. This book provides an overview of Field Effect Transistors (FETs) by discussing the basic principles of FETs and exploring the latest technological developments in the field. It covers and connects a wide spectrum of topics related to semiconductor device physics, physics of transistors, and advanced transistor concepts. This book contains six chapters. Chapter 1 discusses electronic materials and charge. Chapter 2 examines junctions, discusses contacts under thermal-equilibrium, metal-semiconductor contacts, and metal-insulator-semiconductor systems. Chapter 3 covers traditional planar Metal Oxide Semiconductor Field Effect Transistors (MOSFETs). Chapter 4 describes scaling-driving technological variations and novel dimensions of MOSFETs. Chapter 5 analyzes Heterojunction Field Effect Transistors (FETs) and also discusses the challenges and rewards of heteroepitaxy. Finally, Chapter 6 examines FETs at molecular scales. Links the discussion of contemporary transistor devices to physical processes Material has been class-tested in undergraduate and graduate courses on the design of integrated circuit components taught by the author Contains examples and end-of-chapter problems Field Effect Transistors, A Comprehensive Overview: From Basic Concepts to Novel Technologies is a reference for senior undergraduate / graduate students and professional engineers needing insight into physics of operation of modern FETs. Pouya Valizadeh is Associate Professor in the Department of Electrical and Computer Engineering at Concordia University in Quebec, Canada. He received B.S. and M.S. degrees with honors from the University of Tehran and Ph.D. degree from The University of Michigan (Ann Arbor) all in Electrical Engineering in 1997, 1999, and 2005, respectively. Over the past decade, Dr. Valizadeh has taught numerous sections of five different courses covering topics such as semiconductor process technology, semiconductor materials and their properties, advanced solid state devices, transistor design for modern CMOS technology, and high speed transistors.

Table of Contents:
Introduction xi 1 Electronic Materials and Charge Transport 1 1.1 Wave/Particle Electrons in Solids 1 1.1.1 Quantum Description of Electrons 3 1.1.2 Band Diagram and Effective-Mass Formalism 6 1.1.3 Density of States Function 7 1.1.4 Conduction and Valence Bands 8 1.1.5 Band Diagram and Free Charge Carriers 10 1.1.6 Supplementary Notes on Band Diagram 11 1.1.7 Bond Model 14 1.2 Electrons, Holes, and Doping in Semiconductors 14 1.2.1 Electrons and Holes 14 1.2.2 Doping 18 1.2.3 Calculation of Ionization Energies in Semiconductors 24 1.3 Thermal-Equilibrium Statistics 25 1.3.1 Fermi–Dirac Statistics 25 1.3.2 Maxwell–Boltzmann Statistics 27 1.3.3 Calculating Electron and Hole Concentration in Nondegenerate Semiconductors 29 1.3.4 Mass Action Law 31 1.3.5 Calculation of Electron and Hole Concentration in a Degenerate Semiconductor 33 1.3.6 Quasi-Fermi Levels 35 1.3.7 Statistics of Dopant Activation Process 35 1.4 Charge-Carrier Transport in Semiconductors 37 1.4.1 Current-Continuity Equation 39 1.4.2 Drift–Diffusion Formalism 40 1.4.3 Characterization of Low Electric-Field Transport Parameters 53 1.4.4 High Electric-Field Drift Transport 54 1.4.5 Thermionic and Field Emission 61 1.5 Breakdown in Semiconductors 66 1.6 Crystallinity and Semiconductor Materials 69 1.6.1 Bravais Lattices 71 1.6.2 Strain and Techniques of Epitaxy 78 1.7 Quantum Transport Phenomena and Scattering Mechanisms in Semiconductors 89 1.7.1 Quantum Phenomena in Carrier Transport: A Snapshot 90 1.7.2 Drude’s Model: A Close-UP 91 1.7.3 Major Scattering Processes 95 Further Reading 109 Solid-State Theory 109 Physics of Semiconductor Devices 109 Semiconductor Materials and Heterostructures 109 Problems 110 Appendix 1.A Derivation of Fermi–Dirac Statistics 111 Further Reading 114 Appendix 1.B Derivation of Einstein Relationship in Degenerate Semiconductors 114 Further Reading 115 Appendix 1.C Strain Tensor 116 2 Junctions 119 2.1 Contacts Under Thermal Equilibrium 119 2.2 Metal–Semiconductor Contacts 121 2.2.1 Band Diagram of an MS Junction 122 2.2.2 SDA 127 2.3 P–N Junctions 149 2.3.1 Thermal-Equilibrium Band Diagram of P–N Junctions 149 2.3.2 Calculation of Potential across P–N Junctions and SDA 151 2.4 Metal–Insulator–Semiconductor System 188 2.4.1 Thermal-Equilibrium Band Diagram of MOS System 189 2.4.2 Biased MOS System 192 2.4.3 Threshold-Voltage Adjustment and Calculations 200 2.4.4 C–V Characteristic of MOS Systems 208 2.5 Current Conduction in the Presence of Band Discontinuities in Junctions 216 2.5.1 Thermionic Emission 216 2.5.2 Field Emission and Thermionic-Field Emission 224 Further Reading 227 Physics of Semiconductor Devices 227 Problems 228 Appendix 2.A Limitations of SDA and the Meaning of Debye Length 229 3 Traditional Planar MOSFETs: Operation, Modeling, and Technology Scaling 231 3.1 Battle of Transistors: MOSFET Versus BJT 232 3.2 Principles of Operation of MOSFETs and Device Modeling: First-Order Principles 236 3.2.1 Modeling of the Operation of Long-Channel MOSFET 238 3.2.2 Modeling of the Operation of Short-Channel MOSFET 250 3.3 Quantum Confinement and Electrostatics of MOSFET 282 3.4 Subthreshold Operation of Short-Channel MOSFET 285 3.5 Limits of Scaling: A Recap 290 Reference 291 Further Reading 291 Physics of Semiconductor Devices 292 Microfabrication Technology and Material Characterization 292 Problems 292 4 From Scaling-Driven Technological Variations to Novel Dimensions in MISFETs 295 4.1 FinFET, UTBSOI, and Other Multiple-Gate FETs 296 4.1.1 Quantitative Assessment of the Advantages of SOI and Multiple-Gate MOSFETs 301 4.1.2 Multiple-Gate MOSFETs: A Complementary Perspective on the Implementation and Physics of Operation 306 4.1.3 Strain Engineering: From Bulk to Multiple-Gate MOSFETs 313 4.1.4 Limitations of the Introduction of III–V Channels to Multiple-Gate and Other Modern CMOS Technologies 320 4.2 Velocity-Modulation Transistor 321 4.2.1 VMT: Basic Principles of Operation 322 4.2.2 Real-Space Transfer: Speed and Functionality 325 4.3 Resonant-Gate and Resonant-Channel Transistors 333 4.3.1 Resonant-Gate Transistor: Principles of Operation 336 4.3.2 Resonant-Channel Transistor: Principles of Operation 343 4.4 Carbon Nanotube FET and FETs Realized on Other Nanotube and Nanowires 346 4.4.1 CNFETs versus MOSFETs: Differences in Principles of Operation and Realization 348 4.4.2 Other Nanotube and Nanowire Transistors 363 4.5 spinFET 365 4.5.1 spinFET: Principles of Operation 365 4.5.2 spinFET: Challenges in Realization 368 References 372 Further Reading 372 Problems 373 5 Heterojunction FETs 375 5.1 Challenges and Rewards of Heteroepitaxy 377 5.1.1 Lattice Matching and the Substrate Challenge 379 5.1.2 Properties of a Few Famous Nonpolar Heterostructures: A Brief Visit 380 5.2 Quantum Phenomena in Semiconductor Heterostructures 385 5.2.1 Electron Behavior in a Triangular Quantum Well 389 5.2.2 Subbands and Two-Dimensional Electron Gas 391 5.2.3 Semiconductor Heterojunctions and Self-Consistent Evaluation 392 5.2.4 Modulation Doping 394 5.3 HFET: Brief Exposé of Design Intricacies 400 5.3.1 Deep Donors and Modulation Doping 407 5.3.2 Threshold-Voltage Calculation in HFET 409 5.3.3 HFET: A Brief Visit to Microfabrication Challenges 414 5.3.4 Hot Electron Applications Among HFETs 416 5.4 Polar III-Nitride HFET 417 5.4.1 Polarization Among III-Nitride Heterostructures 418 5.4.2 Subband Energy Levels and 2DEG Characteristics of Polar AlGaN/GaN Heterojunctions 422 References 427 Further Reading 427 Physics of Heterostructures and High-Speed Transistors 427 Material Properties and Processing of Semiconductor Materials and Heterostructures 427 Problems 428 6 FETs at Molecular Scales 429 6.1 FET: A Change of Paradigm 430 6.2 Resistance Redefined 431 6.3 Evaluation of Current–Voltage Characteristics of a Single Energy-Level Channel FET 440 6.4 From Current Conduction in Single Energy-Level Channels to Definition of Conductance in Macroscale Conductors 444 Further Reading 448 Index 449

About the Author :
Pouya Valizadeh is Associate Professor in the Department of Electrical and Computer Engineering at Concordia University in Quebec, Canada. He received B.S. and M.S. degrees with honors from the University of Tehran and Ph.D. degree from The University of Michigan (Ann Arbor) all in Electrical Engineering in 1997, 1999, and 2005, respectively. Over the past decade, Dr. Valizadeh has taught numerous sections of five different courses covering topics such as semiconductor process technology, semiconductor materials and their properties, advanced solid state devices, transistor design for modern CMOS technology, and high speed transistors.