Semiconductor Physical Electronics

Transcription

1 Semiconductor Physical Electronics

2 MICRODEVICES Physics and Fabrication Technologies Series Editors: Ivor Brodie and Julius J. Murayt SRI International Menlo Park, California ELECTRON AND ION OPTICS Miklos Szilagyi GaAs DEVICES AND CIRCUITS Michael Shur ORIENTED CRYSTALLIZATION ON AMORPHOUS SUBSTRATES E. I. Givargizov THE PHYSICS OF MICROjNANO-FABRICATION Ivor Brodie and Julius J. Muray PHYSICS OF SUBMICRON DEVICES David K. Ferry and Robert O. Grondin THE PHYSICS OF SUBMICRON LITHOGRAPHY Kamil A. Valiev SEMICONDUCTOR LITHOGRAPHY Principles, Practices, and Materials Wayne M. Moreau SEMICONDUCTOR PHYSICAL ELECTRONICS Sheng S. Li t Deceased. A Continuation Order Plan is available for this series. A continuation order will bring delivery of each new volume immediately upon publication. Volumes are billed only upon actual shipment. For further information please contact the publisher.

3 Semiconductor Physical Electronics Sheng S. Li Department of Electrical Engineering University of Florida Gainesville, Florida Plenum Press New York and London

4 Ll, Shang S S.. lconductor physlc.' electronic. I Shlng S. L1. p. c -- (Mlcrod,vlclS 1 Includ.. bl~llographlcal reflrenc.. and Indl 1. S,.lconductors. 2. Solid Uatl physics. 1. Tltll. II. Serl TK L dc CIP ISBN-13: DOl: / e-isbn-13: Plenum Press, New York Softcover reprint of the hardcover 1st edition 1993 A Division of Plenum Publishing Corporation 233 Spring Street, New York, N.Y. loon All rights reserved No part of this book may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, e1ectronic, mechanical. photocopying. microfilming, recording. or otherwise, without written permission from the Publisher

5 Preface The purpose of this book is to provide the reader with a self-contained treatment of fundamental solid state and semiconductor device physics. The material presented in the text is based upon the lecture notes of a one-year graduate course sequence taught by this author for many years in the Department of Electrical Engineering of the University of Florida. It is intended as an introductory textbook for graduate students in electrical engineering. However, many students from other disciplines and backgrounds such as chemical engineering, materials science, and physics have also taken this course sequence, and will be interested in the material presented herein. This book may also serve as a general reference for device engineers in the semiconductor industry. The present volume covers a wide variety of topics on basic solid state physics and physical principles of various semiconductor devices. The main subjects covered include crystal structures, lattice dynamics, semiconductor statistics, energy band theory, excess carrier phenomena and recombination mechanisms, carrier transport and scattering mechanisms, optical properties, photoelectric effects, metal-semiconductor devices, the p--n junction diode, bipolar junction transistor, MOS devices, photonic devices, quantum effect devices, and highspeed III-V semiconductor devices. The text presents a unified and balanced treatment of the physics of semiconductor materials and devices. It is intended to provide physicists and materials scientists with more device backgrounds, and device engineers with a broader knowledge of fundamental solid state physics. The contents of the text is divided into two parts. In Part I (Chapters 1-9), we cover subjects on fundamental solid state and semiconductor physics that are essential for device applications. In Part II (Chapters 10-15), we deal with basic device physics and structure, operation principles, general characteristics, and the applications of various semiconductor devices. Chapter I presents the classification of solids, crystal structures, the concept of reciprocal lattice and Brillouin lone, the definition of Miller indices, chemical bondings, and crystal defects. Chapter 2 deals with the thermal properties and lattice dynamics of crystalline solids. The lattice specific heat, the dispersion relation of lattice vibrations, and the concept of phonons are also described. Chapter 3 is concerned with the derivation of the three semiconductor statistics, namely, the Maxwell-Boltzmann (M-B), Bose-Einstein (B-E), and Fermi Dirac (F-D) distribution functions. Chapter 4 covers energy band theory, the concept of effective mass, and the density-of-states function for the bulk semiconductor and the superlattice. Chapter 5 describes the equilibrium properties of both the intrinsic and extrinsic semiconductors. Derivation of electron and hole densities, and a discussion of the properties of shallowand deep-level impurities are also covered. Chapter 6 presents the excess carrier phenomenon and recombination mechanisms in a semiconductor. The six basic equations which govern the transport of excess electrons and holes in a semiconductor are described. Chapter 7 is conv

6 PREFACE cerned with the derivation of transport coefficients from the Boltzmann equation, and lowfield galvanomagnetic effects in a semiconductor. Chapter 8 deals with various scattering mechanisms in a semiconductor. The relaxation time and mobility expressions for ionized and neutral impurity scattering, acoustic and optical phonon scattering are derived. Chapter 9 is concerned with the optical properties and photoelectric effects in a semiconductor. The fundamental optical absorption and free carrier absorption processes, the photoconductive, photovoltaic, and photomagnetoelectric effects in a semiconductor are also discussed. Chapter 10 covers the basic physical principles and properties of metal-semiconductor contacts. Both the Schottky barrier and ohmic contacts on a semiconductor are discussed. Carrier transport in a Schottky barrier diode, methods of determining and modifying the barrier height, and the formation of ohmic contacts are presented. Chapter II deals with the basic device theory and properties of a p-n junction diode and a junction-field effect transistor (JFET). Chapter 12 is concerned with the device physics, the structure and characteristics of various photonic devices such as photodetectors, solar cells, light emitting diodes (LEOs) and diode lasers. Chapter 13 describes the bipolar junction transistor (BJTs) and p-n-p-n four-layer devices (e.g., SCRs or thyristers). Chapter 14 presents the silicon-based metal-oxide-semiconductor (MOS) devices. The device physics and characteristics for both the MOS field-effect transistors (MOSFETs) and charge-coupled devices (CCDs) are also described. Finally, in Chapter IS. we cover some novel high-speed devices using GaAs and other III-V compound semiconductors. These include GaAs-based metal-semiconductor field effect transistors (MESFETs). high electron mobility transistors (HEMTs), heterojunction bipolar transistors (HBTs), and transferred electrc?n devices (TEDs). Throughout the text. the author stresses the importance of relating fundamental solid state physics to the properties and performance of various semiconductor devices. Without a good grasp of the physical concepts and an understanding of the underlying device physics. it would be difficult to tackle the problems encountered in material growth and device fabrication. The information presented in this book should provide a solid background for understanding the fundamental physical limitations of semiconductor materials and devices. This book is especially useful for those who are interested in itrengthening and broadening their basic knowledge of solid state and semiconductor device physics. The author would like to acknowledge his former students for the many useful discussions and comments on the text. In particular. he is grateful to Drs. D. H. Lee and C. S. Yeh. and Robert Huang, for their assistance in the preparation of illustrations and the solutions manual, and the proofreading of the manuscript. He is indebted to his son. Jim, for setting up the MicroTex and TEXtures programs with which this book was prepared, and to his wife, Jean, and daughters Grace and Jeanette for their love and support during the course of preparing this book. Gainesville, Florida Sheng S. Li

7 Contents CHAPTER 1. Classification of Solids and Crystal Structure 1.1. Introduction... I 1.2. The Bravais Lattice The Crystal Structure Miller Indices and the Unit Cell The Reciprocal Lattice and Brillouin Zone Types of Crystal Bindings... II 1.7. Defects in a Crystalline Solid Vacancies and Interstitials Line and Surface Defects Problems Bibliography CHAPTER 2. Lattice Dynamics 2.1. Introduction The One-Dimensional Linear Chain Dispersion Relation for a Three-Dimensional Lattice Concept of Phonons The Density of States and Lattice Spectrum Lattice Specific Heat Elastic Constants and Velocity of Sound Problems References Bibliography CHAPTER 3_ Semiconductor Statistics 3.1. Introduction Maxwell-Boltzmann (M-B) Statistics Fermi-Dirac (F-D) Statistics vii

8 viii CONTENTS 3.4. Bose-Einstein (B-E) Statistics Statistics in the Shallow-Impurity States Problems Bibliography CHAPTER 4. Energy Band Theory 4.1. Introduction The Bloch-Floquet Theorem The Kronig-Penney Model The Nearly-Free Electron Approximation The Tight-Binding (LCAO) Approximation The Simple Cubic Lattice The Body-Centered Cubic Lattice (the s-like states) Energy Band Structures for Semiconductors The Effective Mass Concept Energy Band Structure and Density of States in a Superlattice Problems References Bibliography CHAPTER 5. Equilibrium Properties of Semiconductors 5.1. Introduction Densities of Electrons and Holes in a Semiconductor Intrinsic Semiconductors Extrinsic Semiconductors Ionization Energy of a Shallow Impurity Level Hall Effect, Hall Mobility, and Electrical Conductivity... '" Heavy Doping Effects in a Degenerate Semiconductor..., 107 Problems Reference... III Bibliography III CHAPTER 6_ Excess Carrier Phenomenon in Semiconductors 6.1. Introduction Nonradiative Recombination: Shockley-Read-Hall Model Band-to-Band Radiative Recombination Band-to-Band Auger Recombination Basic Semiconductor Equations Charge-Neutrality Conditions The Haynes-Shockley Experiment Minority Carrier Lifetimes and Photoconductivity Experiment Surface States and Surface Recombination Velocity Deep-Level Transient Spectroscopy (DLTS) Technique

9 CONTENTS Ix Surface Photovoltage (SPV) Technique Problems References Bibliography CHAPTER 7. Transport Properties of Semiconductors 7.1. Introduction Galvanomagnetic, Thermoelectric, and Thermomagnetic Effects Electrical Conductivity ITn Electronic Thermal Conductivity Kn... lsi Thermoelectric Coefficients Galvanomagnetic and Thermomagnetic Coefficients Boltzmann Transport Equation... ISS 7.4. Derivation of Transport Coefficients Electrical Conductivity IT Hall Coefficient RH Seebeck Coefficient S Nernst Coefficient Qn Transverse Magnetoresistance Transport Coefficients for the Mixed Conduction Case Electrical Conductivity IT Hall Coefficient RH Seebeck Coefficient S Nernst Coefficient Q Transport Coefficients for Some Semiconductors Problems References Bibliography CHAPTER 8. Scattering Mechanisms and Carrier Mobilities in Semiconductors 8.1. Introduction Differential Scattering Cross Section Ionized Impurity Scattering Neutral Impurity Scattering Acoustic Phonon Scattering Deformation Potential Scattering Piezoelectric Scattering Optical Phonon Scattering... '" Scattering by Dislocations Electron and Hole Mobilities in Semiconductors \ 8.9. Hot Electron Effects in a Semiconductor Problems References Bibliography

10 x CONTENTS CHAPTER 9. Optical Properties and Photoelectric Effects 9.1. Optical Constants of a Solid Free-Carrier Absorption Process Fundamental Absorption Process...,..., Direct Transition Process Indirect Transition Process The Photoconductive Effect Kinetics of Photoconduction Practical Applications of Photoconductivity The Photovoltaic (Dember) Effect The Photomagnetoelectric Effect Problems References... " 245 Bibliography CHAPTER 10. Metal-Semiconductor Contacts Introduction Metal Work Function and Schottky Effect Thermionic Emission Theory Ideal Schottky Barrier Contact Current Flow in a Schottky Barrier Diode... 25(j Thermionic Emission Model Image Lowering Effect The Diffusion Model I-V Characteristics of a Silicon and a GaAs Schottky Diode Determination of Barrier Height Enhancement of Effective Barrier Height Applications of Schottky Diodes Photodetectors and Solar Cells Schottky-Clamped Transistors Microwave Mixers Ohmic Contacts Problems References Bibliography CHAPTER 11. p-n Junction Diodes Introduction Equilibrium Properties of a p-n Junction Diode p-n Junction Under Bias Conditions Minority Carrier Distribution and Current Flow Diffusion Capacitance and Conductance Minority Carrier Storage and Transient Behavior II. 7. Zener and Avalanche Breakdowns Tunnel Diode p-n Heterojunction Diodes...,

11 CONTENTS xl Junction Field-Effect Transistors Problems.... References.... Bibliography CHAPTER 12. Photonic Devices Introduction Photovoltaic Devices p-n Junction Solar Cells Schottky Barrier and MIS Solar Cells Heterojunction Solar Cells Thin Film Solar Cells Photodetectors p-n Junction Photodiodes p-i n Photodiodes Avalanche Photodiodes Schottky Barrier Photodiodes... '" Point-Contact Photodiodes Heterojunction Photodiodes Photomultipliers Long-Wavelength Infrared Detectors Light-Emitting Diodes (LEDs) Injection Mechanisms Electronic Transitions Luminescent Efficiency and Injection Efficiency Application of LEDs..., Semiconductor Laser Diodes Population Inversion...,., Oscillation Conditions Threshold Current Density... " GaAs Laser Diodes Semiconductor Laser Materials Applications of Lasers Problems References Bibliography CHAPTER 13. Bipolar Junction Transistor Introduction Basic Structures and Modes of Operation... " Current-Voltage Characteristics Current Gain, Base Transport Factor, and Emitter Injection Efficiency Modeling of a Bipolar Junction Transistor Switching Transistor Advanced Bipolar Transistor

12 xli CONTENTS Thyristors Problems References Bibliography CHAPTER 14. Metal-Oxide-Semiconductor Field-Effect Transistors 14. \. Introduction An Ideal Metal-Oxide-Semiconductor System \' Surface Space-Charge Region Capacitance-Voltage Characteristics Oxide Charges and Interface Traps \. Interface Trap Charges Oxide Charges... : The MOS Field-Effect Transistors \. General Characteristics of a MOSFET Channel Conductance Current-Voltage Characteristics Small-Signal Equivalent Circuit Scaled-Down MOSFETs Charge-Coupled Devices Charge Storage and Transfer Charge Injection and Detection Buried-Channel CCDs Problems References Bibliography CHAPTER IS. Higb-Speed III-V Semiconductor Devices 15. \. Introduction Metal-Semiconductor Field-Effect Transistors \. Basic Device Structure and Characteristics Current-Voltage Characteristics Small-Signal Device Parameters Second-Order Effects in a GaAs MESFET Modulation-Doped Field-Effect Transistors (MODFETs) \. Equilibrium Properties of the 2-DEG in GaAs DEG Charge Control Regime Current-Voltage Characteristics Heterojunction Bipolar Transistor Device Structure and Fabrication Technology Current Gain and Device Parameters Current-Voltage Characteristics High-Frequency Perfonnance Hot Electron Transistors Resonant Tunneling Devices

13 CONTENTS xiii Transferred-Electron Devices Problems.... References.... Bibliography Index

14 Semiconductor Physical Electronics