Table Of ContentGaAs
DEVICES AND CIRCUITS
MICRODEVICES
Physics and Fabrication Technologies
Series Editors: Ivor Brodie and Julius J. Muray
SRI International
Menlo Park, Calijornia
GaAs DEVICES AND CIRCUITS
Michael Shur
SEMICONDUCTOR LITHOGRAPHY
Principles, Practices, and Materials
Wayne M. Moreau
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GaAs
DEVICES AND CIRCUITS
Michael Shur
University 0/ Minnesota
Minneapolis, Minnesota
Springer Science+Business Media, LLC
Library of Congress Cataloging in Publication Data
Shur, Michael.
GaAs devices and circuits.
(Microdevices: physics and fabrication technologies)
Includes bibliographical references and index.
1. Gallium arsenide seipiconductors. I. Title. 11. Series: Microdevices.
TK7871.15.G3S55 1986 621.3815'2 86-25323
ISBN 978-1-4899-1991-5 ISBN 978-1-4899-1989-2 (eBook)
DOI 10.1007/978-1-4899-1989-2
First Printing - August 1987
Second Printing-September 1988
Third Printing-July 1989
© 1987 Springer Science+Business Media New York
Originally published by Plenum Press, New York in 1987.
Softcover reprint ofthe hardcover 1st edition 1987
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
To the memory of my father,
Saul Shur
Preface
GaAs devices and integrated circuits have emerged as leading contenders for
ultra-high-speed applications. This book is intended to be a reference for a rapidly
growing GaAs community of researchers and graduate students. It was written over
several years and parts of it were used for courses on GaAs devices and integrated
circuits and on heterojunction GaAs devices developed and taught at the University
of Minnesota.
Many people helped me in writing this book. I would like to express my deep
gratitude to Professor Lester Eastman of Cornell University, whose ideas and
thoughts inspired me and helped to determine the direction of my research work
for many years. I also benefited from numerous discussions with his students and
associates and from the very atmosphere of the pursuit of excellence which exists
in his group.
I would like to thank my former and present co-workers and colleagues-Drs.
Levinstein and Gelmont of the A. F. Ioffe Institute of Physics and Technology,
Professor Melvin Shaw of Wayne State University, Dr. Kastalsky of Bell Communi
cations, Professor Gary Robinson of Colorado State University, Professor Tony
Valois, and Dr. Tim Drummond of Sandia Labs-for their contributions to our joint
research and for valuable discussions. My special thanks to Professor Morko.;, for
his help, his ideas, and the example set by his pioneering work.
Since 1978 I have been working with engineers from Honeywell, Inc.-Drs.
Nick Cirillo, Max Helix, Steve Jamison, Andy Peczalski, T. C. Lee, Chente Chao,
Jon Abrokwah, Dave Arch, Obert Tufte, Bob Daniels, Peter Roberts, David Lamb,
and Don Long, Mr. Tho Vu, and others-and have spent with them countless hours
discussing GaAs-related issues and working on GaAs devices and integrated circuits.
I would like to thank them for their help and for creating an environment of
intellectual challenge.
Over the years I have presented my work at different institutions. I would like
to thank Drs. Hans Rupprecht, Paul Solomon, Norm Braslau, Marshai Nathan, and
Bob Rosenberg of IBM, Dr. Dick Eden of Gigabit Logic, Dr. Zucca of Rockwell
International, Dr. Zu leeg of McDonnell Douglas, Dr. Kim of Ford Microelectronics,
Dr. Jim Oakes of Westinghouse, Drs. S. S. Pei and S. Luryi of AT&T Bell Labs,
and Dr. Conwell of Xerox for suggestions and comments.
This book would not have been possible without my former and present graduate
students-Drs. Kwyro Lee, Tzu-Hung Chen, Kang Lee, Chong Hyun, Chung-Hsu
Chen, and many others. I would also like to express my thanks to the students who
took my courses on GaAs devices and circuits at the University of Minnesota, for
vii
vüi PREFACE
their enthusiasm and encouragement, and to Messrs. Pailu Wang, Jingming Xu,
lun-ho Baek, Phil Jenkins, and Young Byun for reading parts of the manuscript.
I would like to thank my colleagues-faculty members at the Department of
Electrical Engineering of the University of Minnesota.
I am thankful to the Microelectronics and Information Sciences Center, and
the Supercomputer Institute at the University of Minnesota, for their continuous
support of our research.
My wife, Paulina Shur, provided me with indispensable support over the years,
helping me enormously with this project in many different ways. And I would like
to finish this Preface with my wife's favorite quote from Thomas Mann:
Again and further are the right words, for the unresearchable plays a kind of rnocking
game with our research ardours; it offers apparent holds and goals, behind which, when
we have gained thern, new reaches of the past still open out-as happens to the coastwise
voyager, who finds no end to his joumey, for behind each headland of clayey dune he
conquers, fresh headlands and new distances lure hirn on.
Michael Shur
Minneapolis. Minnesota
Contents
CHAPTER 1. Chemical Bonds and Crystal Structure
1-1. Atomic States ................................... . . . . . . . . . . . . . 1
1-2. Chemical Bonds. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1-3. Crystal Structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
CHAPTER 2. Band Structure and Transport Properties
2-1. Band Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2-2. The Boltzmann Transport Equation .. . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2-3. Scattering Rates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2-3-1. Polar Optical Scattering ................................. 24
2-3-2. Acoustic Scattering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
2-3-3. Impurity Scattering ..................................... 28
2-3-4. Intervalley Scattering between Nonequivalent Valleys. . . . . . . . 28
2-3-5. Intervalley Scattering between Equivalent Valleys . . . . . . . . . . . 29
2-4. Monte Carlo Simulation . .. . . .. . .. . .. . . . .. .. .. . . .. . .. . . .. .. . .. . 29
2-5. Electron and Hole Mobilities and Drift Velocities . . . . . . . . . . . . . . . . . 37
2-6. Maxwellian and Displaced Maxwellian Distribution Functions and
Phenomenological Transport Equations. . . . . . . . . . . . . . . . . . . . . . . . . . 45
2-7. Phenomenological Equations Based on the Field Dependent Velo city
and Diffusion ................................................ 48
2-8. Energy-Dependent Relaxation Times and Phenomenological Transport
Equations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
2-9. Electron Transport in Small Semiconductor Devices. . . . . . . . . . . . . . . 53
2-9-1. Low-Field Electron Transport in a Uniform Sampie . . . . . . . . . 55
2-9-2. Electron Transport in Short n+ -n-n+ and n+ -p-n+ Structures 64
2-9-3. Overshoot and Ballistic Transport in High Electric Field . . . . . 80
CHAPTER 3. GaAs Technology
3-1. Gallium and Arsenic .......................................... 105
3-2. Crystal Growth of Bulk Material. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
3-3. Liquid Epitaxy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
Ix
x CONTENTS
3-4. Vapor Epitaxy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
3-5. Metal-Organic Chemical Vapor Deposition. . . . . . . . . . . . . . . . . . . . . . 114
3-6. Molecular Beam Epitaxy ...................................... 116
3-7. Characterization of Epitaxial Layers ............................ 121
3-7-1. Determination of Layer Thickness ........................ 121
3-7-2. Determination of Doping Profile from C-V Measurements... 123
3-7-3. Resistivity and Hall Measurements . . . . . . . . . . . . . . . . . . . . . . . . 125
3-7-4. Deep Level Transient Spectroscopy ....................... 127
3-7-5. Film Characterization by Beam Interaction Techniques ...... 134
3-8. Schottky Contacts ............................................ 138
3-8-1. Schottky Barriers ....................................... 138
3-8-2. Current-Voltage Characteristics (Thermionic Emission Model) 142
3-8-3. Current-Voltage Characteristics. Thermionic Field Emission
and Field Emission ..................................... 144
3-8-4. Small Signal Circuit of Schottky Diode. . . . . . . . . . . . . . . . . . . . 145
3-8-5. Practical Schottky Contacts .............................. 146
3-9. Ohmic Contacts .............................................. 147
3-9-1. Minimum Specific Contact Resistance ............ . . . . . . . . . 147
3-9-2. Alloyed, Implanted, and Heterojunction Ohmic Contacts .... 148
3-9-3. Fabrication of Alloyed Contacts . . . . . . . . . . . . . . . . . . . . . . . . . . 151
3-9-4. Resistance of Planar Ohmic Contacts . . . . . . . . . . . . . . . . . . . . . . 152
3-10. Characterization of Ohmic Contacts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
3-10-1. Cox-Strack Technique. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
3-10-2. TLM (Transmission Line Model) Measurements . . . . . . . . . . . 158
3-10-3. Four-Point Method .................................... 159
3-11. Ion Implantation. . . .. .. .... ....... ....... .... ........ ... .. .. . 160
CHAPTER 4. Ridley-Watkins-Hilsum-Gunn Effed
4-1. Introduction ................................................. 173
4-2. High Field Domains .......................................... 176
4-3. Stable Amplification Regime ................................... 179
4-4. Small Signal Analysis ......................................... 182
4-5. Small Signal Impedance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
4-6. Analytical Theory of Stable High Field Domains ................. 187
4-7. Domain Dynamies... ... .... .... ... ... ... ............. ... .. .. . 194
4-8. Aeeumulation Layers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
4-9. Stationary Anode Domains .................................... 204
4-10. Multidomain Regime. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
4-11. Infiuenee of Inhomogeneities and Contacts ...................... 208
4-11-1. Infiuenee of Inhomogeneities . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
4-11-2. Infiuenee of Contaets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
4-12. Domains in Thin Sampies ..................................... 212
4-13. Breakdown in High Field Domains ............................. 215
4-14. Instabilities and High Field Domains in a Semieonductor with Eleetrons
and Holes ................................................... 224
4-14-1. Small Signal Analysis .................................. 224
4-14-2. High Field Domains ................................... 228
4-15. Infiuenee of Magnetie Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236
