Nanostructuring for Nitride Light-Emitting Diodes and Optical Cavities (eBook)

Parts of this thesis have been published in the following journal articles: 6
Supervisor's Foreword 7
Contents 9
Abbreviations 12
1 Introduction 15
1.1 III--V Nitrides 15
1.2 Motivations 16
1.3 Objective and Organization of This Dissertation 17
References 18
2 Background 19
2.1 LED Efficiency 19
2.1.1 Injection Efficiency 19
2.1.2 Internal Quantum Efficiency 20
2.1.3 Light Extraction Efficiency 20
2.2 Strategies for Light Extraction 20
2.2.1 Total Internal Reflection 21
2.2.2 Surface Roughing 22
2.2.3 MicroLEDs 22
2.2.4 Geometrical Shaping 23
2.2.5 Photonic Crystal 24
2.3 Lasing Mechanisms 26
2.4 Quality Factor and Loss of a Resonant Cavity 27
2.5 Nanosphere Lithography 28
2.5.1 Overview 29
2.5.2 Process Development 29
References 31
3 III-Nitride Light-Emitting Diodes with Photonic Crystal Structures 34
Abstract 34
3.1 InGaN Light-Emitting Diodes with Indium Tin Oxide Photonic Crystal Current-Spreading Layer 34
3.1.1 Introduction 35
3.1.2 Experimental Details 35
3.1.3 Surface Morphologies 37
3.1.4 Device Characterizations 37
3.1.5 Theoretical Simulations 40
3.1.6 Conclusion 43
3.2 III-Nitride Light-Emitting Diode with Embedded Photonic Crystal 43
3.2.1 Introduction 44
3.2.2 Experimental Details 45
3.2.3 Optical Properties of Photonic Crystal 45
3.2.4 Raman Spectroscopy 48
3.2.5 Device Characterizations 50
3.2.6 Strain Analysis 53
3.2.7 Conclusion 55
3.3 Air-Spaced GaN Nanopillar Photonic Bandgap Structures 55
3.3.1 Introduction 56
3.3.2 Experimental Details 57
3.3.3 Designing the PhC Structure 59
3.3.4 Fabrication and Optical Characterization of the PhC Structure 60
3.3.5 Enhancement of PL Intensity in PhC Structures 62
3.3.6 The Effects of Disordering in Nanopillar Arrays 63
3.3.7 Conclusion 66
3.4 Tunable Clover-Shaped GaN Photonic Bandgap Structures Patterned by Dual-Step NSL 66
3.4.1 Introduction 67
3.4.2 Process Flow 67
3.4.3 Photonic Bandgap Calculation 69
3.4.4 Transmission Measurements 70
3.4.5 Angular-Resolved PL Measurements 72
3.4.6 Time-Resolved PL Measurements 73
3.4.7 Conclusion 74
3.5 Chapter Summary 74
References 75
4 Whispering Gallery Mode Lasing from Sphere-Patterned Cavities 77
Abstract 77
4.1 Overview 77
4.2 UV Single-Mode Lasing from Metal-Clad Pillar 79
4.2.1 Fabrication Process 79
4.2.2 Optical Properties 79
4.2.3 FDTD Simulation 83
4.2.4 Angular-Resolved PL Spectroscopy 84
4.2.5 Conclusion 85
4.3 High-Q WG Mode from Nanoring Array 85
4.3.1 Process Flow 85
4.3.2 Lasing Characteristics 87
4.3.3 FDTD Simulation 90
4.3.4 Conclusion 91
4.4 Chapter Summary 92
References 92
5 1- mu m Micro-Lens Array on Flip-Chip LEDs 93
Abstract 93
5.1 Introduction 93
5.2 Experimental Details 94
5.3 Device Characterizations 96
5.4 Far-Field Angular-Resolved Measurement 97
5.5 Near-Field Emission Patterns Captured by Confocal Microscopy 100
5.6 Chapter Summary 103
References 103
6 Optical and Thermal Analyses of Thin-Film Hexagonal Micro-Mesh Light-Emitting Diodes 105
Abstract 105
6.1 Introduction 105
6.2 Experimental Details 106
6.3 Electrical Characteristics 108
6.4 Optical Properties 110
6.5 Thermal Analyses 112
6.6 Chapter Summary 114
References 115
7 Conclusion and Future Work 116
7.1 Conclusion 116
7.2 Future Work 117