Silicon Photonics, 2 Volume Set Fundamentals and Applications

Preface xi

Volume 1

1. Introduction to Silicon Photonics 1
1.1 Introduction 1
1.2 VLSI: Past, Present, and Future Roadmap 3
1.3 The Interconnect Problem in VLSI 4
1.4 The Long-Haul Optical Communication Link 7
1.5 Data Network 11
1.6 Conclusions 12
1.7 Scope of the Book 12

2. Basic Properties of Silicon 21
2.1 Introduction 22
2.2 Band Structure 22
2.3 Density-of-States Function 32
2.4 Impurities 35
2.5 Alloys of Silicon and Other Group IV Elements 38
2.6 Heterojunctions and Band Lineup 41
2.7 Si-Based Heterostructures 43
2.8 Direct Gap: Ge/SiGeSn Heterojunctions 58

3. Quantum Structures 71
3.1 Introduction 71
3.2 Quantum Wells 71
3.3 Quantum Wires and Dots 83
3.4 Superlattices 88
3.5 Silicon-Based Quantum Structures 91
3.6 Effect of Electric Field 101

4. Optical Processes 109
4.1 Introduction 109
4.2 Optical Constants and Electromagnetic Wave Propagation 110
4.3 Basic Concepts 114
4.4 Absorption Processes in Semiconductors 117
4.5 Fundamental Absorption in Direct Bandgap Semiconductors 119
4.6 Fundamental Absorption in Indirect-Gap Semiconductors 128
4.7 Absorption and Gain in Semiconductors 134
4.8 Intervalence Band Absorption 138
4.9 Free-Carrier Absorption 139
4.10 Recombination and Luminescence 143
4.11 Nonradiative Recombination 150
4.12 Excitonic and Impurity Absorption 157

5. Optical Processes in Quantum Structures 167
5.1 Introduction 167
5.2 Optical Processes in QWs 168
5.3 Intersubband Transitions 180
5.4 Excitonic Processes in QWs 186
5.5 Effect of Electric Fields 194
5.6 Optical Processes in QWRs 199
5.7 Optical Processes in QDs 202
5.8 Optical Processes in Si QWRs and QDs 205

6. Light Emitters in Si 211
6.1 Introduction 211
6.2 Basic Principles of Light Emission in Semiconductors 212
6.3 Early Approaches-Zone Folding in Si-Ge Superlattices 215
6.4 Band Structure Engineering Using Alloys 217
6.5 Quantum Confinement 220
6.6 Impurities in Silicon 229
6.7 Stimulated Emission: Prospect 237
6.8 Intersubband Emission 242
6.9 Tensile-Strained Ge Layers 248
6.10 GeSn Lasers: Toward Silicon-Compatible Light Sources 251

7. Si Light Modulators 263
7.1 Introduction 263
7.2 Physical Effects 265
7.3 Electrorefraction in Silicon 273
7.4 Thermo-Optic Effects in Si 276
7.5 Modulators: Some Key Characteristics 278
7.6 Modulation Bandwidth Under Injection 280
7.7 Optical Structures 282
7.8 Electrical Structures 287
7.9 High-Bandwidth Modulators 294
7.10 Performance of EO Modulators 299
7.11 Summarizing Comments of Performance Metrics 299

8. Silicon Photodetectors 309
8.1 Introduction 309
8.2 Optical Detection 311
8.3 Important Characteristics of Photodetectors 315
8.4 Examples of Types of Photodetectors 326
8.5 Examples of Photodiodes in Standard Silicon Technology 332
8.6 Phototransistors in Standard Silicon Technology 337
8.7 CMOS and BiCMOS 339
8.8 Silicon-on-Insulator 339
8.9 Photodetectors Using Heteroepitaxy 343
8.10 Single-Photon Avalanche Diodes (SPADs) 362

References for Tables 8.1 to 8.3 378
Problems 380
References 382

Volume 2

9. Raman Lasers 387
9.1 Introduction 387
9.2 Raman Scattering: Basic Concepts 390
9.3 Simplified Theory of Raman Scattering 398
9.4 Raman Effect in Silicon 402
9.5 Raman Gain Coefficient 404
9.6 Continuous-Wave Raman Laser 411
9.7 Further Developments, Challenges, and Perspectives in Silicon Raman Lasers 415

10. Guided Light Waves: Introduction 423
10.1 Introduction 423
10.2 Ray-Optic Theory for Light Guidance 424
10.3 Reflection Coefficients 426
10.4 Modes of a Planar Waveguide 428
10.5 Wave Theory of Light Guides 435
10.6 3D Optical Waveguides 445
10.7 Loss Mechanisms in Waveguides 455
10.8 Coupling to Optical Devices 463
10.9 Other Ways of Guiding Light Waves 473

11. Principle of Planar Waveguide Devices 479
11.1 Introduction 479
11.2 Model for Mode Coupling 480
11.3 Directional Coupler 484
11.4 Distributed Bragg Reflector 489
11.5 Some Useful Planar Devices 495

12. Waveguides for Dense Wavelength-Division Multiplexing Systems 519
12.1 Introduction 519
12.2 Structure and Operation of AWGs 521
12.3 AWG Characteristics 526
12.4 Methods for Enhancing AWG Performance 533
12.5 Applications of AWGs 540
12.6 PHASAR-Based Devices on Different Materials 552
12.7 Echelle Grating 557

13. Nonlinear Silicon Photonics 565
13.1 Introduction 565
13.2 Optical Processes and Nonlinearity 565
13.3 Phase Matching and Quasi-Phase Matching 576
13.4 Some Theoretical Aspects of Optical Pulse Propagation 583
13.5 Silicon Structures with Optical Nonlinearity 601
13.6 Optical Nonlinearity in Silicon and Applications 604

14. Fabrication Techniques and Materials Systems 647
14.1 Introduction 647
14.2 Planar Processing 651
14.3 Substrate Growth and Preparation 651
14.4 Material Modification 660
14.5 Etching 666
14.6 Lithography 673
14.7 Fabrication of Waveguides 675
14.8 Grating Formation Process 681
14.9 Materials Systems for Waveguide Formation 685

Questions and Problems 705
References 707
Suggested Reading 710
Appendix A k p Method 713
Appendix B Bra-Ket Notation 741
Appendix C Values of Parameters 753
Index 755