臺灣博碩士論文加值系統

本論文以有機金屬氣相磊晶法製研三族氮化物之光電元件。首先使用製程改善方式來提升氮化鎵藍色發光二極體之發光效率。側邊粗化與微米尺度導光柱之表面粗化結構應用於氮化鎵藍色發光二極體上，藉由降低元件內部全反射可有效提升發光效率約26%。再者，結合反射式金屬p/n型電極-銀/鉻/金(Ag/Cr/Au)、側邊粗化及微米尺度導光柱之表面粗化結構與圖案化藍寶石基板於氮化鎵發光二極體上，其光電轉換效率可較傳統之氮化鎵發光二極體提升約80%。
成長氮化鎵/氮化鋁鎵多層結構於圖案化n型氮化鎵上，利用材料其光學折射係數差異形成之散射層(light scattering layer)可有效提升發光二極體發光效率約30%。此外，同質性(homogeneous)成長之氮化鎵磊晶層於圖案化n型氮化鎵上，因其側向與縱向成長速率之差異形成一類似側向磊晶成長模式(Epitaxial lateral overgrowth model)也可有效改善磊晶薄膜品質。
成長單層結構之氮化鋁鎵薄膜於具微米柱結構之圖案化氮化鎵上，因不同磊晶成長平面形成的表面應力與成長速率之差異，而存在有一相異鋁含量之分佈。利用其結構特性製作氮化鋁鎵系列蕭特基光檢測器可得到雙吸收波段為326nm和346nm，而其分別來自於微米柱平台與邊緣側壁之氮化鋁鎵的吸收。

In this dissertation, growth and fabrication of III-nitride-based optoelectronic devices by MOVPE have been studied. Several methods used to improve output power efficiency of GaN-based blue light emitting diodes (LEDs) have been studied. GaN-based blue LEDs with textured sidewalls and micro-scale pillars around mesa region could enhance light efficiency about 26% by reducing the total internal reflection of light inside the LED structure. Furthermore, comparison of conventional LEDs, the LEDs combining with textured sidewalls, GaN micro-pillars around the mesa region, patterned sapphire substrate (PSS), and highly reflective p-/n-type Ag/Cr/Au electrode pads could further improve around 80% in wall-plug efficiency (WPE).
The embedded multilayers of GaN/AlxGa1-xN microlens-like structure on GaN template with micro-pillars pattern could enhance the LEDs output power by more than 30% due to the enhanced guided-light scattering efficiency, resulting from the difference in refractive index of GaN and AlGaN layer. Moreover, owing to the difference in lateral and vertical growth rate of homoepitaxial GaN grown on GaN template with micro-pillars pattern, the similar epitaxial lateral overgrowth model have be demonstrated and could further improve the crystal quality of epilayer.
A single AlGaN layer with two different Al contents by grown on the GaN template with micro-pillars structure has been demonstrated. The strains-induced Al incorporation efficiency and difference in lateral and vertical growth rate of AlGaN grown on the sidewalls, top and valley surfaces of the pillars lead to form the different Al contents in the single AlGaN layer. The Schottky-type photodetectors (PDs) were also demonstrated for double Al contents of deposited AlGaN on GaN μ-pillar templates, exhibiting the three steps of responses occurred at about 326, 346, and 356 nm. The cutoff wavelength of the Schottky PDs at 326 and 346 nm should be contributed by the AlGaN layer on the sidewall of cone shaped pillars and the rest of the area of the AlGaN, respectively.

摘要 I
Abstract III
Acknowledgement V
Contents VI
Table Captions IX
Figure Captions X

Chapter 1 Introduction 1
1.1 Properties and applications of wide bandgap III-Nitride semiconductors 1
1.2 Background of wide bandgap III-Nitride semiconductors 7
1.3 Organization of this dissertation 13
References in chapter 1 14

CHAPTER 2 Metalorganic Vapor Phase Epitaxy System 22
2.1 Introduction 22
2.2 The Basic Reaction of GaN Epitaxy Process in MOVPE 23
2.3 MOVPE System 26
2.3.1 Gas Delivery System 26
2.3.2 Reactor System 27
2.3.3 Exhaust System 28
2.4 In-Situ Monitoring for Epitaxy Growth 29
Reference in chapter 2 32

CHAPTER 3 The Study of Light Output Power Improvement in III-Nitride Based Light Emitting Diodes 36
3.1 Introduction 36
3.2 III-Nitride Based Light Emitting Diodes with GaN Micro-Pillars around Mesa and Patterned Substrate 38
3.3 GaN-Based LEDs with GaN μ-Pillars Around Mesa, Patterned Substrate, and Reflector Under Pads 58
References in chapter 3 67

Chapter 4 GaN-based Light Emitting Diodes with microlens-like structure by grown on GaN template with Micro-Pillar structure 71
4.1 Introduction 71
4.2 Growth and fabrication of GaN-based LEDs on GaN template with micro-pillar structure 73
4.3 Characteristics of GaN-based LEDs with embedded microlens-like structure 81
References in chapter 4 94

Chapter 5 AlGaN-based Ultraviolet Photodetector with Micro-Pillar structures 97
5.1 Introduction 97
5.2 Characteristics of AlGaN grown on GaN template with micro-pillar patterned structure 98
5.3 Characteristics of AlGaN-based ultraviolet photodetector with micro-pillar structures 106
References in chapter 5 114

Chapter 6 Conclusions and Future works 116
6.1 Conclusions 116
6.2 Future works 118

Publication List 120

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