臺灣博碩士論文加值系統

　　本論文針對氮化鎵系列的發光二極體，在亮度輸出方面在一系列的探討，藉此能夠找出最好之方式來增加光的輸出。在此篇論文上，我們提出各種不同的製程方式來增加光的輸出，包含不同的透明接觸電極、抗反射層、高反射層、類似共振腔發光二極體、不同圖案、覆晶發光二極體。
　　在透明電極方面，我們採用二種不同的金屬製程，一種是一般傳統的鎳/金製程，另一種則是銦氧錫製程。在兩個比較中，我們發現銦氧錫製程對於光的輸出有很大的幫助，但對於電性方面則呈現較差之狀態。在發光二極體正面，則因為氮化鎵和空氣中的折射係數分別為2.4與1造成在介面上會部分的光會折會回來造成光的損失，故因此在兩個介面面蒸鍍一層二氧化錫藉此提升光之亮度。
　　此外，我們亦在發光二極體背面蒸鍍高反射率的薄膜，藉著高反射率的薄膜能夠使往下的光再反射回去增加光的輸出。另一面，我們亦在上方蒸鍍不同反射率的薄膜，利用共振的原理來增加光的輸出。
另外，我們設計不同的光罩圖樣，使得P電極到N電極的電流流經的途徑一致，能夠達到電流之均勻性，藉此增加光的輸出。最後我們欲利用新的發光二極體結構，因為沒有P電極之遮蔽效應，所以能夠增加光的輸出。

　　In this dissertation, we will discuss a series improvement of output light intensity for GaN-based LED devices to find out the best way to increase the light intensity. In this dissertation, we provide several kinds of processes to increase the output light intensity, include of transparent contact layers, antireflection layers, high reflection layers, similar RCLED (Resonant Cavity LED), different pattern, and Flip Chip LED devices.
　　In transparent contact layers, two different metal processes are used. One is the traditional process Ni/Au, and the other is ITO process. The comparison of Ni/Au and ITO, we find out there is a lot of improvement in output light intensity of ITO process, but there is poor performance in electrical characteristics of ITO process. On topside of LED, the portion of light loss is reflected back at the interface due to the difference of refractive index between GaN (about 2.4) and air (1), therefore, we coat SiO2 between two mediums to increase the light intensity.
　　Besides, the coating high reflectance film on bottom side LED is used to increase the light intensity. The light is reflected back due to high reflectance. The other, we use resonant theory to coat different pair DBR with different reflectance to increase the light intensity.
In addition, we design different mask pattern. These designs making the current paths from P-pad to N-pad obtain a uniform current spreading to increase the light intensity. Finally, the new flip chip structure will increase the light intensity due to no p-pad.

中文摘要 I
Abstract III
致謝 V
Figure Captions VI
Chapter 1. Introduction 1
1.1 THE BACKGROUND OF GAN-BASED LEDS 1
1.2 OVERVIEW OF THIS DISSERTATION 3
Chapter 2. Theoretical study and Simulation 4
2.1 THEORETICAL STUDY 4
2.1.1 Loss mechanisms 4
2.1.2 Antireflection Coating 6
2.1.3 Distributed Bragg reflector (DBR) 8
2.1.4 RCLED (Resonant-Cavity Light-Emitting Diodes) 9
2.1.5 uniform current spreading 9
2.2 SIMULATION 10
2.2.1 DBR 11
Chapter 3 Experiment Procedures and Equipment 12
3.1 THE GROWTH OF GAN-BASED LEDS DEVICES 12
3.2 THE PROCEDURES OF GAN-BASED LEDS CHIPS 12
3.2.1 Wafer cleaning: 13
3.2.2 Mesa etching: 13
3.2.3 P-type contact layer: 13
3.2.4 n-type contact layer: 14
3.2.5 Passivation/Antireflective SiO2 coating: 14
3.2.6 wafer lapping and polish 14
3.2.8 Wafer scribe 14
3.3 EQUIPMENT 15
3.3.1 MOCVD 15
3.3.2 ICP system 15
Chapter 4. Result and Discussion 17
4.1 TRANSPARENT CONTACT LAYER 17
4.1.1 Transmittance of Ni/Au and ITO 17
4.1.2 Light Output Intensity of Ni/Au and ITO 18
4.2 ANTIREFLECTION LAYERS COATED LED 18
4.2.1 The Transmittance of Antireflection Layers 18
4.2.2 Light Output Intensity of Antireflection Layers 19
4.3 HIGH REFLECTION LAYERS BOTTOM COATED LED 19
4.3.1 The Reflectance of Reflection Layers 19
4.3.2 Light Output Intensity of Reflectance Layers 19
4.4 RCLED (RESONANT CAVITY LED) DEVICE 20
4.5 DIFFERENT PATTERN TO INCREASE THE LIGHT INTENSITY 21
4.6 FLIP CHIP DEVICE 22
Chapter 5. Conclusion and Future Work 24
5.1 CONCLUSION 24
5.2 FUTURE WORK 25
References 26

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