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Contents
1 Introduction 1
References 5
2 Basic Principles of LED 7
2.1 LED Luminescence Principle 7
2.1.1 History and Principle of Lighting Source 7
2.1.2 p-n Junction and the Principle of LED Luminescence 8
2.2 Radiation and Non-radiation Recombination 10
2.3 LED Optical and Electrical Characteristics 11
2.3.1 LED Quantum Efficiency 11
2.3.2 Radiation Spectrum 12
2.3.3 Basic Photometric Concepts in LED 14
2.3.4 Electrical Characteristics of LED 14
2.4 Principle ofWhite LED 15
2.4.1 The Principle of Three Primary Colors and Addition of Light 15
2.4.2 The Realization Method of White LED 15
References 17
3 Properties and Testing of Group III-Nitride LED Materials 19
3.1 Crystal Structure and Band Structure of Group III Nitride 19
3.1.1 Crystal Structure 19
3.1.2 Band Structure 21
3.2 Polarization Effect of Group III Nitride Materials 23
3.2.1 Polarization Effect 23
3.2.2 Influence of Polarization Effect 24
3.3 Doping of Group III-Nitride LEDMaterials 25
3.3.1 Doping of Nitride LEDMaterials 25
3.4 Test and Analysis of the Properties of Group III Nitride Materials 26
3.4.1 Structural and Morphological Analysis 26
3.4.2 Surface and Film Composition Analysis 28
3.4.3 Other Photoelectric Test Methods 30
References 32
4 Epitaxial of III-Nitride LED Materials 33
4.1 Basic Models of Epitaxial 33
4.1.1 3-D Growth Mode (Volmer-Weber Mode) 34
4.1.2 2-D Growth Mode (Frank-Vander Merwe Mode) 34
4.1.3 2-D and 3-D Mixed Growth Mode(Stranski-Krastanob Mode) 35
4.2 Substrate for Epitaxial Growth of III-Nitride LEDs(Sapphire/Si/SiC/LiAlO2/GaN) 36
4.3 Group III Nitride LED Epitaxial Technology 38
4.3.1 LPEMethod 38
4.3.2 MBEMethod 39
4.3.3 MOCVDMethod 39
4.3.4 HVPEMethod 47
4.4 Two-Step Growth Method for MOCVD Grown Nitride Materials 48
4.4.1 Surface Dynamics for Film Growth 48
4.4.2 Two-Step Growth Program for GaN/Sapphire by MOCVD 51
4.5 Influence of Growth Conditions on Epitaxial Layer Quality of Group III NitrideMaterials 53
4.5.1 Effect of Buffer Layer Growth Conditions on Material Quality 54
4.5.2 Effect of Rough Layer Growth Conditions 63
4.6 Epitaxial Technology of High Quality GaN on SiC Substrate 64
4.6.1 Basic Properties of SiC 64
4.6.2 Nucleation and Growth of GaN on SiC Substrate 66
4.6.3 Roots of GaN Stress on SiC Substrates 70
References 71
5 InGaN/GaN Multiple Quantum Wells Materials as Well as Blue and Green LEDs 75
5.1 Introduction to InGaN Material System 76
5.2 Polarization Effects in InGaN/GaN Multiple Quantum WellsMaterials 77
5.2.1 Polarity of GaN-BasedMaterials 77
5.2.2 Spontaneous Polarization and Piezoelectric Polarization 78
5.3 Quantum-Confined Stark Effect 82
5.3.1 Effect on Transition Energy Levels 83
5.3.2 Effect on Luminous Intensity 84
5.4 Carrier Localization in InGaN/GaN Multiple Quantum Wells 84
5.5 Green LED and Non-polar£¬ Semi-polar LED 86
5.5.1 Polar Surface High in Composition Green LEDs 87
5.5.2 Semi-polar and Non-polar Materials 88
5.5.3 Research Progress on Semi-polar and Non-polar LEDs 89
References 90
6 AlGaN-Based Multiple-Quantum-Well Materials and UV LEDs 93
6.1 Introduction of AlGaN Material System 94
6.2 Optical and Electrical Properties of AlGaN Materials 97
6.3 Epitaxial Growth and Doping Techniques for AlGaN Materials 98
6.4 Structure Design and Fabrication of UV LEDs 103
References 108
7 III-Nitride LED Quantum Efficiency Improvement Technology 113
7.1 Three Structures of LED 113
7.2 Internal Quantum Efficiency Improvement Technology 116
7.2.1 Homo-Epitaxial Growth of GaN 116
7.2.2 Multiple Quantum Wells 118
7.2.3 Active Region Doping 122
7.2.4 Electronic Barrier Layer 122
7.3 Light Extraction Efficiency Improvement Technology 124
7.3.1 Patterned Sapphire Substrate 124
7.3.2 Surface Roughening 128
7.3.3 Reflector 130
7.3.4 Flip-Chip Structure 133
7.3.5 Photonic Crystal 134
7.4 Current Injection Efficiency Improvement Technology 134
7.4.1 Current Spreading Layer 135
7.4.2 Current Distribution Theory 136
7.4.3 Current Blocking Technique 140
7.5 Droop Effect 141
7.5.1 Auger Recombination Effect 143
7.5.2 Electronic Overflow 144
References 147
8 III-Nitride LED Chip Fabrication Techniques 151
8.1 Group III Nitride LED Fabrication Process 151
8.2 Photolithography 152
8.2.1 Mask and Photoresist 153
8.2.2 Lithography Process 154
8.3 Etching Process 157
8.3.1 Etching Parameters 158
8.3.2 Wet Etching and Dry Etching 158
8.3.3 Etching of GaNMaterials 159
8.3.4 Etching of ITO and SiO2 Materials 160
8.4 Evaporation and Sputtering 161
8.4.1 Metal Evaporation 161
8.4.2 SiO2 Passivation Layer 162
8.5 Ohmic Contacts 163
8.5.1 n-type GaN Ohmic Contact 163
8.5.2 p-type GaN Ohmic Contact 164
8.5.3 Specific Contact Resistivity 165
8.5.4 Transparent Electrode Technolog