Series Editors Arthur Willoughby University of Southampton, Southampton, UK Peter Capper Ex???Leonardo MW Ltd, Southampton, UK Safa Kasap University of Saskatchewan, Saskatoon, Canada

Edited by Stuart Irvine, PhD, DSc College of Engineering, Swansea University, UK Peter Capper, PhD Ex-Leonardo MW Ltd, Southampton, UK

List of Contributors xv Foreword xvii Series Preface xix Preface xxi Safety and Environment Disclaimer xxiii 1 Introduction to Metalorganic Vapor Phase Epitaxy 1S.J.C. Irvine and P. Capper 1.1 Historical Background of MOVPE 1 1.2 Basic Reaction Mechanisms 4 1.3 Precursors 8 1.4 Types of Reactor Cell 9 1.5 Introduction to Applications of MOVPE 11 1.5.1 AlN for UV Emitters 11 1.5.2 GaAs/AlGaAs VCSELS 11 1.5.3 Multijunction Solar Cells 12 1.5.4 GaAs and InP Transistors for High¿Frequency Devices 13 1.5.5 Infrared Detectors 14 1.5.6 Photovoltaic and Thermophotovoltaic Devices 14 1.6 Health and Safety Considerations in MOVPE 15 1.7 Conclusions 16 References 16 2 Fundamental Aspects of MOVPE 19G.B. Stringfellow 2.1 Introduction 19 2.2 Thermodynamics 20 2.2.1 Thermodynamics of MOVPE Growth 20 2.2.2 Solid Composition 24 2.2.3 Phase Separation 29 2.2.4 Ordering 31 2.3 Kinetics 35 2.3.1 Mass Transport 35 2.3.2 Precursor Pyrolysis 36 2.3.3 Control of Solid Composition 37 2.4 Surface Processes 40 2.4.1 Surface Reconstruction 41 2.4.2 Atomic¿Level Surface Processes 42 2.4.3 Effects of Surface Processes on Materials Properties 44 2.4.4 Surfactants 46 2.5 Specific Systems 52 2.5.1 AlGaInP 52 2.5.2 Group III Nitrides 53 2.5.3 Novel Alloys 56 2.6 Summary 59 References 60 3 Column III: Phosphides, Arsenides, and Antimonides 71H. Hardtdegen and M. Mikulics 3.1 Introduction 71 3.2 Precursors for Column III Phosphides, Arsenides, and Antimonides 73 3.3 GaAs¿Based Materials 74 3.3.1 (AlGa)As/GaAs Properties and Deposition 74 3.3.2 GaInP, (AlGa)InP/GaAs Properties and Deposition 79 3.4 InP¿Based Materials 82 3.4.1 InP Properties and Deposition 82 3.4.2 AlInAs/GaInAs/AlGaInAs Properties and Deposition 83 3.4.3 AlInAs/GaInAs/InP Heterostructures 84 3.4.4 InxGa1-xAsyP1-y Properties and Deposition 84 3.5 Column III Antimonides Properties and Deposition 86 3.5.1 Deposition of InSb, GaSb, and AlSb 87 3.5.2 Deposition of Ternary Column III Alloys (AlGa)Sb and (GaIn)Sb 89 3.5.3 Deposition of Ternary Column V Alloys In(AsSb), GaAsSb 89 3.5.4 Deposition of Quaternary Alloys 90 3.5.5 Epitaxy of Electronic Device Structures 90 3.5.6 Epitaxy of Optoelectronic Device Structures 95 3.6 In Situ Optical Characterization/Growth Control 100 3.7 Conclusions 100 References 101 4 Nitride Semiconductors 109A. Dadgar and M. Weyers 4.1 Introduction 109 4.2 Properties of III¿Nitrides 110 4.3 Challenges in the Growth of III¿Nitrides 111 4.3.1 Lattice and Thermal Mismatch 111 4.3.2 Ternary Alloys: Miscibility and Compositional Homogeneity 113 4.3.3 Gas¿Phase Prereactions 115 4.3.4 Doping of III¿Nitrides 117 4.4 Substrates 120 4.4.1 Heteroepitaxy on Foreign Substrates 122 4.4.2 GaN Growth on Sapphire 125 4.4.3 III¿N Growth on SiC 126 4.4.4 GaN Growth on Silicon 127 4.5 MOVPE Growth Technology 130 4.5.1 Precursors 130 4.5.2 Reactors and In Situ Monitoring 130 4.6 Economic Importance 136 4.6.1 Optoelectronic Devices 137 4.6.2 Electronic Devices 138 4.7 Conclusions 138 References 138 5 Metamorphic Growth and Multijunction III¿V Solar Cells 149N.H. Karam, C.M. Fetzer, X.¿Q. Liu, M.A. Steiner, and K.L. Schulte 5.1 Introduction to MOVPE for Multijunction Solar Cells 149 5.1.1 III¿V PV Solar Cell Opportunities and Applications 149 5.1.2 Metamorphic Multijunction Solar Cells 151 5.1.3 Reactor Technology for Metamorphic Epitaxy 154 5.2 Upright Metamorphic Multijunction (UMM) Solar Cells 154 5.2.1 Introduction and History of Upright Metamorphic Multijunctions 154 5.2.2 MOVPE Growth Considerations of UMM 156 5.2.3 Growth and Device Results 158 5.2.4 Challenges and Future Outlook 162 5.3 Inverted Metamorphic Multijunction (IMM) Solar Cells 162 5.3.1 Introduction and History of Inverted Metamorphic Multijunctions 162 5.3.2 MOVPE Growth Considerations of IMM 164 5.3.3 Growth and Device Results 167 5.3.4 Challenges and Future Outlook 169 5.4 Conclusions 169 References 170 6 Quantum Dots 175E. Hulicius, A. Hospodková, and M. Zíková 6.1 General Introduction to the Topic 175 6.1.1 Definition and History 175 6.1.2 Paradigm of Quantum Dots 176 6.1.3 QD Types 176 6.2 AIIIBV Materials and Structures 178 6.2.1 QDs Embedded in the Structure 178 6.2.2 Semiconductor Materials for Embedded QDs 180 6.3 Growth Procedures 181 6.3.1 Comparison of MBE¿ and MOVPE¿Grown QDs 181 6.3.2 Growth Parameters 182 6.3.3 QD Surrounding Layers 185 6.4 In Situ Measurements 193 6.4.1 Reflectance Anisotropy Spectroscopy of QD Growth 193 6.4.2 Other Supporting In Situ Measurements 197 6.5 Structure Characterization 198 6.5.1 Optical: Photo¿, Magnetophoto¿, Electro¿luminescence, and Spin Detection 198 6.5.2 Microscopies - AFM, TEM, XSTM, BEEM/BEES 200 6.5.3 Electrical: Photocurrent, Capacitance Measurements 202 6.6 Applications 203 6.6.1 QD Lasers, Optical Amplifiers, and LEDs 204 6.6.2 QD Detectors, FETs, Photovoltaics, and Memories 205 6.7 Summary 208 6.8 Future Perspectives 208 Acknowledgment 209 References 209 7 III¿V Nanowires and Related Nanostructures: From Nitrides to Antimonides 217H.J. Joyce 7.1 Introduction to Nanowires and Related Nanostructures 217 7.2 Geometric and Crystallographic Properties of III¿V Nanowires 219 7.2.1 Crystal Phase 219 7.2.2 Growth Direction, Morphology, and Side¿Facets 220 7.3 Particle¿Assisted MOVPE of Nanowires 222 7.3.1 The Phase of the Particle 222 7.3.2 The Role of the Particle 224 7.3.3 Axial and Radial Growth Modes 226 7.3.4 Self¿Assisted Growth 228 7.4 Selective¿Area MOVPE of Nanowires and Nanostructures 228 7.4.1 The Role of the Mask 229 7.4.2 Axial and Radial Growth Modes 230 7.5 Alternative Techniques for MOVPE of Nanowires 231 7.6 Novel Applications of Nanowires 231 7.7 Concluding Remarks 233 References 234 8 Monolithic III/V integration on (001) Si substrate 241B. Kunert and K. Volz 8.1 Introduction 241 8.2 III/V¿Si Interface 243 8.2.1 Si Surfaces 243 8.2.2 Interface Formation in the Presence of Impurities and MO Precursors 247 8.2.3 Atomic III/V on Si Interface Structure 249 8.2.4 Antiphase Domains 251 8.2.5 III/V Growth on Si(001) 252 8.3 Heteroepitaxy of Bulk Layers on Si 255 8.3.1 Lattice¿Matched Growth on Si 257 8.3.2 Metamorphic Growth on Blanket Si 258 8.3.3 Selective¿Area Growth (SAG) on Si 264 8.4 Conclusions 282 References 282 9 MOVPE Growth of Cadmium Mercury Telluride and Applications 293C.D. Maxey, P. Capper, and I.M. Baker 9.1 Requirement for Epitaxy 293 9.2 History 294 9.3 Substrate Choices 295 9.3.1 Orientation 296 9.3.2 Substrate Material 296 9.4 Reactor Design 297 9.4.1 Process Abatement Systems 298 9.5 Process Parameters 299 9.6 Metalorganic Sources 299 9.7 Uniformity 300 9.8 Reproducibility 302 9.9 Doping 302 9.10 Defects 304 9.11 Annealing 307 9.12 In Situ Monitoring 308 9.13 Background for Applications of MOVPE MCT 308 9.13.1 Introduction to Infrared Imaging and Atmospheric Windows 308 9.13.2 MCT Infrared Detector Market in the Modern Era 309 9.14 Manufacturing Technology for MOVPE Photodiode Arrays 311 9.14.1 Mesa Heterojunction Devices (MHJ) 311 9.14.2 Wafer¿Scale Processing 312 9.15 Advanced MCT Technologies 312 9.15.1 Small¿Pixel Technology 313 9.15.2 Higher Operating Temperature (HOT) Device Structures 313 9.15.3 Two¿Color Array Technology 314 9.15.4 Nonequilibrium Device Structures 316 9.16 MOVPE MCT for Scientific Applications 316 9.16.1 Linear¿Mode Avalanche Photodiode Arrays (LmAPDs) in MOVPE 316 9.17 Conclusions and Future Trends for MOVPE MCT Arrays 320 Definitions 321 References 322 10 Cadmium Telluride and Related II¿VI Materials 325G. Kartopu and S.J.C. Irvine 10.1 Introduction and Historical Background 325 10.2 CdTe Homoepitaxy 327 10.3 CdTe Heteroepitaxy 327 10.3.1 InSb 327 10.3.2 Sapphire 328 10.3.3 GaAs 329 10.3.4 Silicon 330 10.4 Low¿Temperature Growth and Alternative Precursors 330 10.5 Photoassisted MOVPE 332 10.6 PlasmäAssisted MOVPE 333 10.7 Polycrystalline MOCVD 333 10.8 In Situ Monitoring of CdTe 334 10.8.1 Mechanisms for Laser Reflectance (LR) Monitoring 335 10.9 MOCVD of CdTe for Planar Solar Cells 337 10.9.1 CdS and CdZnS Window Layers 338 10.9.2 CdTe Absorber Layer 338 10.9.3 CdCl2 Treatment Layer 342 10.9.4 Photovoltaic Planar Devices 343 10.10 Core¿Shell Nanowire Photovoltaic Devices 345 10.11 Inline MOCVD for Scaling of CdTe 347 10.12 MOCVD of CdTe for Radiation Detectors 350 References 351 11 ZnO and Related Materials 355V. Muñoz¿Sanjosé and S.J.C. Irvine 11.1 Introduction 355 11.2 Sources for the MOCVD Growth of ZnO and Related Materials 356 11.2.1 Metalorganic Zinc Precursors 356 11.2.2 Metalorganic Cadmium Precursors 360 11.2.3 Metalorganic Magnesium Precursors 360 11.2.4 Precursors for Oxygen 361 11.2.5 Precursors for Doping 363 11.3 Substrates for the MOCVD Growth of ZnO and Related Materials 364 11.3.1 ZnO Single Crystals and ZnO Templates as Substrates 365 11.3.2 Sapphire (Al2O3) 367 11.3.3 Silicon 369 11.3.4 Glass Substrates 372 11.4 Some Techniques for the MOCVD Growth of ZnO and Related Materials 373 11.4.1 Atmospheric and Low¿Pressure Conditions in Conventional MOCVD Systems 374 11.4.2 MOCVD¿Assisted Processes 376 11.5 Crystal Growth of ZnO and Related Materials 380 11.5.1 Crystal Growth by MOCVD of ZnO Layers 380 11.5.2 Crystal Growth of ZnO Nanostructures 393 11.5.3 Crystal Growth of ZnO¿Related Materials 398 11.5.4 Doping of ZnO and Related Materials 400 11.6 Conclusions 405 Acknowledgments 406 References 406 12 Epitaxial Systems for III¿V and III¿Nitride MOVPE 423W. Lundin and R. Talalaev 12.1 Introduction 423 12.2 Typical Engineering Solutions Inside MOVPE Tools 424 12.2.1 Gas¿Blending System 424 12.2.2 Exhaust System 433 12.2.3 Reactors 435 12.3 Reactors for MOVPE of III¿V Materials 438 12.3.1 General Features of III¿V MOVPE 438 12.3.2 From Simple Horizontal Flow to Planetary Reactors 439 12.3.3 Close¿Coupled Showerhead (CCS) Reactors 445 12.3.4 Rotating¿Disk Reactors 447 12.4 Reactors for MOVPE of III¿N Materials 451 12.4.1 Principal Differences between MOVPE of Classical III¿Vs and III¿Ns 451 12.4.2 Rotating¿Disk Reactors 454 12.4.3 Planetary Reactors 455 12.4.4 CCS Reactors 458 12.4.5...