CVD of Compound Semiconductors: Precursor Synthesis, Development and Applications

349 Pages·1997·11.339 MB·English

by  Prof. Anthony C. Jones, Prof. Paul O'Brien(auth.)

Anthony C. Jones
Paul O’Brien
CVD of Compound
Semiconductors
Further Reading from VCH
T. T. Kodas, M. J. Hampden-Smith (Eds.)
The Chemistry of Metal CVD
ISBN 3-527-29071-0
W. S. Rees, Jr. (Ed.)
CVD of Nonmetals
ISBN 3-527-29295-0
K. J. Bachmann
The Materials Science of Microelectronics
ISBN 0-89573-280-7
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Published six times a year as a part of
Advanced Materials by VCH
ISSN 0948-1907
Anthony C. Jones, Paul O’Brien
CVD of Compound
Semiconductors
Precursor Synthesis,
Development and Applications
Prof. Anthony C. Jones Prof. Paul O’Brien
Rosetree Cottage, Georgian Close Department of Chemistry
Eccleston Park Imperial College of Science, Technology and Medicine
Prescot South Kensington
Merseyside L35 7JW London SW7 2AY
United Kingdom United Kingdom
This book was carefully produced. Nevertheless, authors and publisher do not warrant the infor-
mation contained therein to be free of errors. Readers are advised to keep in mind that statements,
data, illustrations, procedural details or other items may inadvertently be inaccurate.
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Production Manager: Claudia Gross1
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A catalogue record for this book is available from the British Library
Die Deutsche Bibliothek - CIP-Einheitsaufnahme
Jones, Anthony C.:
CVD of compound semiconductors : precursor synthesis,
development and applications / Anthony C. Jones ; Paul O’Brien. -
Weinheim ;N ew York ; Basel ; Cambridge ; Tokyo : VCH, 1997
ISBN 3-527-29294-2
NE: O’Brien, Paul:
0 VCH Verlagsgesellschaft mbH, D-69451 Weinheim (Federal Republic of Germany), 1997
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Compound semiconductors - usually based on a combination of Group 111-V or 11-VI
elements - have had a significant impact on our everyday lives. A wide variety of
applications exist, including use in satellite TV receivers, optical fiber communications,
CD-players, bar code readers and full-color electroluminescent advertising displays.
Metalorganic chemical vapor deposition (MOCVD), which uses a volatile metalorganic
compound to deposit solid semiconductor films, has become one of the preferred
industrial techniques for the fabrication of sophisticated devices from 111-V and 11-VI
materials, and the application of metalorganic chemistry has played a vital role.
The rapid development of MOCVD owes a great deal to collaboration between
different scientific disciplines such as chemistry, physics, materials science, and engi-
neering. This book is intended to promote continued dialogue between scientists from
different research areas. It is aimed at the chemist who wants to learn more about crystal
growth, and the crystal grower who wants to appreciate the chemical background to his
activity. The book has been written with the practising scientist in mind, although the
text and references should prove useful to those who have only recently entered the
field. Also, certain aspects of the text may be used in chemistry and materials science
courses at undergraduate and postgraduate level.
Basic concepts are covered in Chapter 1, which will be useful to the chemist entering
the materials area. Chapter 2 details general methods for the synthesis, purification, and
characterization of the chemical precursors and will provide chemical background for
the materials scientist. Chapters 3 and 4 discuss in detail the application of precursors in
the MOCVD of 111-V and 11-VI materials, respectively. The related vapor phase tech-
niques of chemical beam epitaxy (CBE) and atomic layer epitaxy (ALE) are described in
Chapters 5 and 6, respectively. Finally, we look to the possible future use of single-
source precursor molecules in Chapter 7.
The concept for the book arose out of a fruitful long-term collaboration between
Epichem Ltd and university departments at Queen Mary and Westfield College and,
more recently, Imperial College of Science, Technology and Medicine. The book ap-
proaches the subject from the perspective of chemists actively involved in developing
precursors for the deposition of such materials. We hope that other similar industrial-
academic links are stimulated and that further ideas are suggested for applying metal-
organic chemistry to CVD.
We would like to acknowledge the significant contribution of the Directors and staff
of Epichem Limited and research students at Queen Mary and Westfield College and
Imperial College. We are also indebted to our many colleagues in the field of semicon-
ductor CVD and Katherin Sanderson for editorial assistance. We are especially grateful
to our wives, Christine Jones and Kym O’Brien, without whose support this book could
not have been written.
January 1997 Tony Jones
Paul O’Brien
The Authors
Tony Jones trained as an organometallic chemist at the University of Manchester, where
he received both his B. Sc. (1976) and Ph. D. (1979). From 1980-1983 he undertook
post-doctoral research at the University of Liverpool into the development of novel
synthetic routes to main-group organometallic compounds for use in MOCVD. He was a
co-founder of Epichem Ltd., established in 1983 specifically to manufacture chemicals
for the semiconductor industry. He is currently Principle Scientific Consultant to Epi-
chem and Chief Scientist at Inorgtech Ltd. He also holds Visiting Professorships at the
University of Salford and the Imperial College of Science, Technology and Medicine
London. In 1996 he received the Michael A. Lunn Outstanding Contributor Award for
research on precursors for indium phosphide and related materials. His current research
interests include the development of precursors for the CVD of compound semiconduc-
tors, metals, metal oxides and metal nitrides. He is a committee member of the Applied
Solid State Chemistry Group of the Royal Society of Chemistry and a Fellow of the
Royal Society of Chemistry.
Paul O’Brien graduated with a B.Sc. from the University of Liverpool in 1975 and
received a Ph. D. from University College Cardiff in 1978 and then moved directly to a
lecturing post in inorganic chemistry at Chelsea College of Science and Technology,
University of London. The macro-restructuring of the Chemistry Departments within
the University of London led to a move to Queen Mary College (QMC) in 1984. Close
involvement with the late Mark Faktor and Don Bradley led to an interest in materials
chemistry and especially novel routes for the deposition of 11-VI materials and a long
standing collaboration with Epichem. Promoted to a chair at QMC in 1994, an almost
immediate move to Imperial College as a Professor of Inorganic Chemistry followed.
The O’Brien group is at present involved in developing precursor chemistry for a wide
range of materials. There is still a keen interest in 11-VI compounds but also work on
oxides, 111-V materials and a rapidly expanding interest in nanodispersed materials for
the electronics industry. He is a Fellow of the Royal Society of Chemistry (R.S.C.), a
member of the American Chemical Society, hon. Secretary of the Applied Solid State
Chemistry Group of the R.S.C., a member of the Materials Forum of the R.S.C. and a
member of the Society of the Chemical Industries Material Group Committee.
Contents
1 Basic Concepts ............................................ 1
1.1 Introduction ............................................... 1
1.2 Compound Semiconductors .................................. 2
1.3 Description of the Band Gap ................................. 4
1.3.1 Density of States ........................................... 4
1.3.2 Extrinsic Semiconductors .................................... 5
1.3.3 Characterizing Carrier Concentrations .......................... 7
1.3.4 Direct and Indirect Band Gaps ................................ 9
1.3.5 Photoluminescence Spectroscopy .............................. 10
1.3.6 p-n Junctions .............................................. 12
1.4 General Structural Properties of Compound Semiconductors ....... 13
1.5 Applications of III-V Semiconductors .......................... 15
1.5.1 Light Emitting Diodes ....................................... 16
1.5.2 Solid State Lasers .......................................... 18
1.6 Structural Properties and Applications of II-VI Semiconductors .... 19
1.7 III-VI Semiconductors ...................................... 22
1.8 Vapor Phase Techniques ..................................... 23
1.8.1 Methods of Crystal Growth .................................. 23
1.8.2 Historical Perspective ....................................... 26
1.8.3 Basic Principles of MOVPE. CBE and ALE .................... 29
1X 3.1 Metalorganic Vapor Phase Epitaxy (MOVPE) ................... 29
1.8.3.2 Chemical Beam Epitaxy ..................................... 36
1.8.3.3 Photoassisted Processes ...................................... 39
1.8.3.4 Atomic Layer Epitaxy (ALE) ................................ 40
1.9 References ................................................ 40
2 Precursor Chemistry ....................................... 43
2.1 Introduction ............................................... 43
2.2 Group IIIA Metalorganic Precursors ........................... 46
2.2.1 Aluminum Chemistry ....................................... 46
2.2.2 Gallium ................................................... 50
2.2.3 Indium ................................................... 54
2.2.4 Group I11 Metal Alkyl Adducts ............................... 56
2.2.5 Metalorganic Precursor Purity ................................ 58
VIII Contents
2.3 Analysis Techniques ........................................ 61
2.3.1 Determination of Trace Metal Impurities ........................ 61
2.3.2 Determination of Organic Impurities ........................... 63
2.3.3 Identification of Impurities in the Semiconductor Layer ........... 64
2.4 Purification of Group I11 Trialkyl Compounds ................... 65
2.4.1 Classical Purification Techniques .............................. 66
2.4.2 Adduct Purification Techniques ............................... 70
2.5 Group I1 Metalorganic Precursors ............................. 76
2.5.1 Dialkylzinc Compounds ..................................... 76
2.5.2 Other Group I1 Metalorganic Precursors ........................ 81
2.6 Purification of Group I1 Precursors ............................ 81
2.6.1 Adduct Purification of Group I1 Metalorganic Precursors .......... 81
2.7 Compounds of Phosphorus. Arsenic and Antimony ............... 83
2.7.1 Alkylarsenic Compounds .................................... 83
2.7.2 Alkyl Phosphorus Hydrides .................................. 84
2.7.3 Alkylantimony Compounds .................................. 85
2.8 Group VI Metalorganic Precursors ............................. 86
2.8.1 Compounds of Sulfur. Selenium. and Tellurium .................. 86
2.9 Thermal Stability of Metalorganic Precursors .................... 87
2.9.1 DSC Data for Group I11 Metalorganics ......................... 88
2.9.2 Base-Free Trialkyls. R, M .................................... 89
2.9.3 Adducts of Group I11 Trialkyls ................................ 92
2.9.4 Precursors Containing an Al-Hydride Bond ..................... 93
2.9.5 DSC Data for Group I1 Alkyls .............................
2.9.6 Conclusions ............................................... 95
2.10 References ................................................ 95
3 MOVPE of 111-V Compounds ............................... 99
3.1 Introduction ............................................... 99
3.2 Growth of Gallium Arsenide (GaAs) ........................... 100
3.2.1 Growth Using Conventional Precursors ......................... 100
3.2.1.1 Me,Ga/AsH, .............................................. 100
3.2.1.2 Et,Ga/AsH, ............................................... 103
3.2.2 Growth of GaAs Using Alternative Ga Precursors ................1 06
3.2.3 Growth of GaAs Using Alternative As Precursors ................ 109
3.2.3.1 Precursor Requirements ...................................... 109
3.2.3.2 Trialkylarsenic Precursors .................................... 110
3.2.3.3 Alkylarsenic Hydride Precursors .............................. 111
3.2.3.4 Alternative Arsenic Precursors Containing Other Functional Groups . 11 3
3.3 Growth of Aluminum Gallium Arsenide (AlGaAs) ............... 114
3.3.1 Growth of AlGaAs Using Conventional Precursors ............... 114
3.3.1.1 Carbon Incorporation ........................................ 114
Contents IX
3.3.1.2 Oxygen Incorporation ....................................... 117
3.3.2 Growth of AlGaAs Using Alternative A1 Precursors .............. i19
3.3.2.1 AlGaAs Growth Using Methyl-Based Alternatives ............... 119
3.3.2.2 AlGaAs Growth Using Ethyl-Based Alternatives .................1 22
3.3.2.3 AlGaAs Growth Using Higher A1 Alkyls ....................... 123
3.3.2.4 AlGaAs Growth Using Al-Hydride Precursors ...................1 25
3.3.2.5 AlGaAs Growth Using Coordinatively Saturated Al-Alkyls ........ 127
3.3.2.6 Growth of AlGaAs Using TBA ............................... 128
3.4 Growth of Indium-Based Alloys .............................. 128
3.4.1 Growth Using Conventional Precursors ......................... 128
3.4.2 Growth of InP Using Alternative In Precursors .................. 130
3.4.2.1 Use of Adducts in InP Growth ................................ 130
3.4.2.2 Alternative Liquid Indium Precursors for InP Growth .............1 31
3.4.3 Growth of InP Using Alternative Phosphorus Precursors .......
3.4.3.1 Tertiarybutylphosphine ...................................... 135
3.4.3.2 Alternative RPH. Precursors .................................. 138
3.4.4 Precursors for AlInAs and AlInGaAs Growth .................... 139
3.5 Growth of Antimony-Based Alloys ............................ 141
3.5.1 Antimonide Growth Using Conventional Precursors .............. 142
3.5.2 Alternative Sb Precursors .................................... 142
3.5.3 Alternative Group I11 Precursors for Group III-Antimonide Growth . 15 1
3.6 Growth of Group I11 Nitrides ................................. 154
3.6.1 Growth Using Conventional Precursors ......................... 154
3.6.1.1 Mechanism of Group IIi Nitride Growth from Conventional Sources 155
3.6.2 Growth of Group I11 Nitrides Using Alternative Precursors ........ 159
3.6.2.1 Alternative Nitrogen Sources ................................. 159
3.6.2.2 Alternative Group 111 Precursors .............................. 163
3.6.3 Conclusions Concerning the Low Temperature Growth of Group I11
Nitrides ................................................... 163
3.7 Metalorganic Dopant Sources for III-V Alloys ..................1 64
3.7.1 Doping of Group I11 Arsenides and Phosphides ..................1 64
3.7.2 Doping of Group I11 Nitrides ................................. 171
3.8 Hydrogen Passivation of Intentional Dopants .................... 171
3.9 Selective Area Epitaxy ...................................... 173
3.10 Photo-Assisted Growth of III-V Materials ...................... 177
3.11 References ................................................ 178
4 MOVPE of II-VI Compounds ............................... 187
4.1 Precursors for Wide Band Gap iI-VI Alloys .................... 187
4.1.1 Introduction ............................................... 187
4.1.2 Growth of Zinc-Based Chalcogenides .......................... 187
4.1.2.1 Alternative Zinc Precursors .................................. 187
X Contents
4.1.2.2 Alternative Group VI Precursors .............................. 193
4.1.3 Metalorganic Dopant Sources for ZnSe and ZnS .................2 02
4.1.4 Precursors for Cadmium-Based Chalcogenides ...................2 07
4.2 Metalorganic Precursors for Narrow Band Gap 11-VI Materials ..... 210
4.2.1 Alternative Organotellurium Precursors for Growth of CdTe and
CdHgTe .................................................. 211
4.2.2 Alternative Cd Precursors for Growth of CdTe and CdHgTe ....... 212
4.2.3 Alternative Hg Precursors .................................... 213
4.2.4 Metalorganic Dopant Sources for CdHgTe and Related Alloys ...... 213
4.2.4.1 n-Type Doping ............................................. 214
4.2.4.2 p-Type Doping ............................................. 214
4.2.4.3 Mn-Doping of Cd-Based Narrow Band Gap Alloys ...............2 17
4.2.5 Reaction Mechanisms in Narrow Gap Alloy Growth ..............2 18
4.3 Photoassisted MOVPE of 11-VI Semiconductors .................2 21
4.3.1 Photodissociation of Group 11 Metal Alkyls ..................... 221
4.3.1.1 Vapor Phase Photodissociation ................................ 221
4.3.1.2 Surface Photodissociation Reactions ........................... 222
4.3.2 Photoepitaxy of CdTe and CdxHg,.xTe .......................... 223
4.3.3 Photoepitaxy of Zn-Based 11-VI Semiconductors .................2 24
4.4 References ................................................ 225
5 Metalorganic Precursors for Chemical Beam Epitaxy .......... 229
5.1 Introduction ............................................... 229
5.2 Growth of GaAs and AlGaAs ................................ 231
5.2.1 Growth Using Conventional Precursors ......................... 231
5.2.1.1 GaAs Growth .............................................. 231
5.2.1.2 AlGaAs Growth ............................................ 234
5.2.2 Growth of GaAs and AlGaAs by CBE Using Alternative
Metalorganic Precursors ..................................... 235
5.2.2.1 Alternative A1 Precursors .................................... 235
5.2.2.2 Alternative Ga Precursors .................................... 237
5.2.2.3 New Routes to Low-Oxygen Content CBE Precursors ............2 48
5.2.2.4 Alternative As Precursors for CBE ............................ 250
5.3 Growth of InP and Related Alloys by CBE ..................... 252
5.3.1 Conventional Precursors ..................................... 252
5.3.2 Growth of In-Based Alloys Using Alternative Precursors ..........2 55
5.3.2.1 Alternative In Sources ....................................... 255
5.3.2.2 Alternative Phosphorus Sources ............................... 257
5.4 Metalorganic Dopant Sources for CBE/MOMBE ................. 259
5.4.1 Doping of GaAs and AlGaAs ................................. 259
5.4.1.1 n-Type Dopant Sources ...................................... 259
5.4.1.2 p-Type Dopant Sources ...................................... 260