INTRODUCTION TO APPLIED SOLID STATE PHYSICS

Transcription

1 INTRODUCTION TO APPLIED SOLID STATE PHYSICS TOPICS IN THE APPLICATIONS OF SEMICONDUCTORS, SUPERCONDUCTORS, AND THE NONLINEAR OPTICAL PROPERTIES OF SOLIDS

2 INTRODUCTION TO APPLIED SOLID STATE PHYSICS TOPICS IN THE APPLICATIONS OF SEMICONDUCTORS, SUPERCONDUCTORS, AND THE NONLINEAR OPTICAL PROPERTIES OF SOLIDS RICHARD DALVEN Department of Physics University of California Berkeley, California PLENUM PRESS NEW YORK AND LONDON

3 Library of Congress Cataloging in Publication Data Dalven, Richard. Introduction to applied solid state physics. Includes bibliographies and index. 1. Solid state physics. 2. Semiconductors. I. Title. QC176.D '028 ISBN-13: : / e-isbn-13: Plenum Press, New York A Division of Plenum Publishing Corporation 227 West 17th Street, New York, N.Y Softcover reprint of the hardcover 1 st edition 1980 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, electronic, mechanical, photocopying, microfilming, recording, or otherwise, without written permission from the Publisher

4 To my father, JOSEPH DALVEN and to the memory of my mother RUTH NEWTON DALVEN

5 Preface The aim of this book is a discussion, at the introductory level, of some applications of solid state physics. The book evolved from notes written for a course offered three times in the Department of Physics of the University of California at Berkeley. The objects of the course were (a) to broaden the knowledge of graduate students in physics, especially those in solid state physics; (b) to provide a useful course covering the physics of a variety of solid state devices for students in several areas of physics; (c) to indicate some areas of research in applied solid state physics. To achieve these ends, this book is designed to be a survey of the physics of a number of solid state devices. As the italics indicate, the key words in this description are physics and survey. Physics is a key word because the book stresses the basic qualitative physics of the applications, in enough depth to explain the essentials of how a device works but not deeply enough to allow the reader to design one. The question emphasized is how the solid state physics of the application results in the basic useful property of the device. An example is how the physics of the tunnel diode results in a negative dynamic resistance. Specific circuit applications of devices are mentioned, but not emphasized, since expositions are available in the electrical engineering textbooks given as references. To summarize, the aim of the book is the physics underlying the applications, rather than the applications themselves. The second key word is survey. The book is designed to be broad rather than deep. Although the survey approach is not to everyone's taste, it has proved popular with the approximately 120 Berkeley graduate students (mostly in physics) who took or audited the course in 1973, 1974, and They seemed to want to learn something, but not everything, about the applications of the solid state physics they already knew. As a survey, the selection of topics is a compromise between recognition of the overwhelming vii

6 viii Preface technological importance of semiconductor devices and a desire to have some breadth of coverage. To this end, about 70% of the material covers applications of semiconductors, and the remainder is divided about evenly between nonlinear optical devices and superconductive materials and devices. Since the physics of the applications is the central interest of the book, no special effort was made to select the latest devices or to indicate the present "state of the art." The book is a textbook ("A textbook explains, a treatise expounds" J. M. Ziman) in that its aim is frankly tutorial. The book is essentially a collection of material from a number of sources, ranging from introductory textbooks to research journals, organized and presented with the intent of emphasizing the basic physics involved. There is no original work included. More advanced treatments and discussions of fine points are left to the literature. However, the reader is provided with references where fuller and/or more advanced treatments may be found. Further, a special effort has been made to give very specific references, telling where values of parameters, etc., were obtained. A selection of problems can be found at the end of each chapter. These are derivations, illustrative calculations, or invitations to explore the physics of some application. It is believed that these points harmonize with the attempt to provide a broad selection of the applications of solid state physics, while telling the reader where further information may be found. The order of the first seven chapters is more or less linear. After a first chapter that is partly review and partly new material that will be useful, Chapter 2 treats the semiconductor p-n junction in some detail. The third chapter exploits this treatment in a discussion of several device applications. Chapter 4 treats the physics of metal-semiconductor and metal-insulatorsemiconductor junctions, and the results are used in Chapter 5 to explore a few applications. In Chapter 6, a potpourri of "other" devices is discussed; they were chosen principally on the basis of my own interests. The seventh chapter treats a number of detectors and generators (principally semiconductors) of electromagnetic radiation. Chapter 8 is mostly concerned with the physics of Josephson junction devices, but concludes with a short discussion of the transition temperature in superconductors. Finally, Chapter 9 covers the interaction of electromagnetic waves in nonlinear solids, and concludes with a few applications. In teaching a course on these topics, I have found that this book contains too much material for a one-quarter course. One semester would seem about right, particularly if appropriate review material were included. The notation used is standard, except perhaps that I have used W for the electric

7 Preface ix field vector to avoid confusion with energy E, particularly in band diagrams. The chapter on nonlinear optics reverts to the more common E for electric field because there seemed little possibility of ambiguity. The presentation relies on a number of standard sources. Charles Kittel's classic introductory text on solid state physics is constantly quoted and used as a reference. Other books on which I have drawn particularly are Solid State Electronic Devices by B. G. Streetman; "Optical Second Harmonic Generation and Parametric Oscillation" by A. Yariv, in Topics in Solid State and Quantum Electronics, W. D. Hershberger (editor); The Feynman Lectures on Physics by R. P. Feynman, R. B. Leighton, and M. Sands; and Long-Range Order in Solids by R. M. White and T. H. Geballe. This book is at the introductory level in that no particular prior knowledge of solid state device physics is assumed. However, the introductory level is not the same for all topics. For example, the treatment of the applications of nonlinear optical effects in solids is more complex than the treatment of the p-n junction. As for prerequisites, it is assumed that the reader has had an introductory course in solid state physics at the level of Kittel's Introduction to Solid State Physics, Fifth Edition. In particular, it is assumed that the reader has a knowledge of energy bands, semiconductors, and superconductivity equivalent to that covered in Chapters 7, 8, and 12 of Kittel's book. In addition, this book assumes a knowledge of electromagnetic theory at the level of Reitz and Milford's Foundations of Electromagnetic Theory, of optics at the level of Stone's Radiation and Optics or Fowles's Modern Optics, and of quantum mechanics at the level of Bohm's Quantum Theory. Many people have shared their expertise with me and have commented on the manuscript at various stages. I would like to thank N. Amer, T. Andrade, B. Black, R. W. Boyd, J. Clarke, M. L. Cohen, L. M. Falicov, L. T. Greenberg, E. L. Hahn, G. I. Hoffer, M. B. Ketchen, A. F. Kip, R. U. Martinelli, R. S. Muller, W. G. Oldham, and P. L. Richards for helping me improve the book. However, the responsibility for errors and misconceptions is mine alone. Special thanks are due M. L. Cohen and C. Kittel for their encouragement during the development of the course. T. H. Geballe kindly provided me with a prepublication copy of his work. I would like to thank M. L. Cohen, D. Long, G. S. Kino, W. F. Oldham, J. Tauc, D. Adler, E. Gutsche, J. Millman, B. G. Streetman, T. C. Harman, H. Y. Fan, and J. Clarke for permission to use figures from their publications. The hospitality extended by John Clarke was invaluable and is sincerely appreciated. Linda Billard typed part of the manuscript with great

8 x Preface skill, and Leslie Hausman typed the first draft. Gloria Pelatowski executed the drawings with exceptional skill and enthusiasm. Last, but also first, I would like to thank D. and G. for making this book a reality. Berkeley, California RICHARD DALVEN

9 Contents 1. Review of Semiconductor Physics Introduction Metals, Insulators, and Semiconductors. Band Structure Diagrams Holes in Semiconductors Effective Mass of Carriers in Semiconductors Conductivity of Semiconductors Carrier Density in an Intrinsic Semiconductor. Impurity Conductivity (Extrinsic Conductivity). Fermi Level Position in Extrinsic Semiconductors Carrier Lifetime in Semiconductors. Problems.... References and Comments The Semiconductor p-n Junction Introduction Qualitative Discussion of the p-n Junction in Equilibrium. 25 Quantitative Treatment of the p-n Junction in Equilibrium. 33 Effect of an Applied Potential on Electron Energy Bands. 48 Diffusion and Recombination of Excess Carriers Qualitative Discussion of a Junction under an Applied Potential 53 Qualitative Discussion of Current Flow in the Biased Junction 57 Quantitative Treatment of Carrier Injection in the Junction 59 Calculation of the Current through the Junction Majority and Minority Carrier Components of the Junction Current. 69 Summary of the Basic Physics of the p-n Junction 72 Reverse Breakdown in p-n Junctions 73 Other Topics on p-n Junctions 75 Problems References and Comments xi

10 Contents 3. Semiconductor p-ii Junction Devices Introduction Semiconductor ~n Junction Diodes. 79 The Bipolar Junction Transistor Amplification in the Bipolar Transistor. 85 Current Gain in the Bipolar Transistor. 86 Circuit Configurations for Amplification with the Bipolar Transistor. 88 Quantitative Discussion of the Bipolar Transistor Summary of the Physics of Amplification in the Bipolar Transistor 96 Tunnel Diodes The Junction Field Effect Transistor (JFET) Physical Basis of the Current-Voltage Characteristic of the JFET. 102 Problems References and Comments. 106 IOd 4.; Pbysics of Metal-Semiconductor and Metal-Insulator-Semiconductor Junctions Introduction The Metal-Semiconductor Junction at Equilibrium.... Effect of an Applied Potential on the Metal-Semiconductor Junction Physics of the Metal-Insulator-Semiconductor Structure Problems.... References and Comments Metal-Semiconductor and Metal-Insulator-Semiconductor Devices Introduction Metal-Semiconductor (Schottky) Diodes The Insulated-Gate Field-Effect Transistor (IGFET) The Induced-Channel MOSFET Summary of the Physics of Field-Effect Transistors Applications of the MOSFET Charge-Coupled Devices.. Problems.... References and Comments Other Semiconductor Devices Introduction Semiconductor Surface States. Band Structure at the Semiconductor Surface

11 Contents Calculation of the Amount etp. of Band Bending.... Effect of Surface States on Metal-Semiconductor Contacts Photoemission from Semiconductors.... Effect of the Surface on Photoemission Negative Electron Affinity in Semiconductors... Physics of the Transferred Electron (Gunn) Effect. Physics of Amorphous Semiconductors Amorphous Semiconductor Devices Problems.... References and Comments. xiii ]51 ] ] Detectors and Generators of Electromagnetic Radiation Introduction Intrinsic Photon Absorption in Semiconductors Photon Absorption by Bound States of Impurities in Semiconductors Threshold Energies for Photon Absorption Photoconductivity in Semiconductors Photodiodes Photovoltaic Devices Other Applications of Intrinsic Photoconductivity Summary on Semiconductor Photon Detectors Emission of Photons in Semiconductors p-n Junction Luminescence Light Amplification by Stimulated Emission of Radiation. Solid State Lasers Semiconductor Injection Lasers Summary on Solid State Lasers Problems.... References and Comments. ] ] ] ]95 ] Superconductive Devices and Materials Introduction Review of Some Aspects of Superconductivity Wave Function of the Condensed Phase of Pairs The Josephson Effects.... Physics of the DC Josephson Effect Physics of the AC Josephson Effect Voltage-Current Curves for Josephson Junctions Effect of Electromagnetic Radiation on the Junction. Quantization of Magnetic Flux in a Superconducting Ring. Superconducting Quantum Interference The Superconducting Quantum Interference Device (Squid). Superconducting Materials: The Transition Temperature

12 xiv Contents Problems References and Comments Physics and Applications of the Nonlinear Optical Properties of Solids Introduction Review of Electromagnetic Wave Propagation in Solids Electric Polarization in an Isotropic Linear Dielectric Solid 260 Nonlinear Polarization and Nonlinear Susceptibility Anharmonic Oscillator Model of a Nonlinear Solid Summary of the Physical Picture of Nonlinear Polarization 270 Tensor Nature of the Nonlinear Susceptibility Solid State Physics Factors Affecting the Nonlinear Susceptibility. 271 Magnitude of the Nonlinear Susceptibility Wave Equation for the Nonlinear Crystal Wave Propagation and Interaction in a Nonlinear Crystal 278 Optical Second Harmonic Generation Phase Matching (Index Matching) in Second Harmonic Generation 292 Frequency Mixing and Up-Conversion 293 Parametric Amplification. 298 Summary Problems References and Comments Appendix: References on Some Other Topics. 309 Author Index. 311 Subject Index