臺灣博碩士論文加值系統

本論文以有機金屬氣相磊晶法成長氮化物半導體材料，並結合選擇性成長技術應用於發光二極體及光偵測器元件。首先利用二氧化矽介電材料當遮蔽層於氮化鎵基板上定義不同大小、形狀及開口率，探討氮化鎵及氮化鋁鎵材料於不同成長條件下的成長機制及負載效應 (loading effect)，建立配合元件結構設計的成長參數。此外，探討二氧化矽和氮化鎵基板經高溫成長過程後，各元素於介面相互擴散情形對歐姆接觸特性的影響。商業化多將氮化鎵材料成長於不導電的藍寶石基板上，因此在元件製作上皆需要多一道乾式蝕刻步驟以利電極製作。利用選擇性成長方式直接定義出發光二極體元件大小，可省略乾式蝕刻製程；而磊晶成長條件使得元件周圍形成特定晶格方向的斜面，能有效的提升光萃取效率。此外，利用此選擇性成長技術得到一非平面的磊晶結構，元件幾何形狀的改變將有助於提升發光二極體電流均勻散佈的潛力。而將此選擇性成長技術應用於氮化鋁鎵系? p-i-n 紫外光偵測器，不僅能夠得到和傳統製程方式相同的元件特性，還能有效減少氮化鋁鎵/氮化鎵異質接面成長所產生的張應力累積，此一特性非常有利於製作高鋁含量之p-i-n 紫外光偵測器。利用此技術更可成長倒置形的氮化鋁鎵系列p-i-n 紫外光偵測器，解決傳統低電阻?的p型氮化鋁鎵材?作為窗戶層，陽極電極製作不易和所導致短波段偵測嚴重的表面吸收問題。

In this dissertation, selective-area grown (SAG) techniques performed by metalorganic vapor phase epitaxy (MOVPE) have been demonstrated to grow GaN-based light emitting diodes (LEDs) and AlGaN-based photodiodes (PDs). The SAG GaN and AlxGa1-xN epitaxial layers are grown on GaN template substrates with SiO2 mask layers. The SiO2–masked GaN templates featured different open window ratios were used to understand the growth mechanisms and establish epitaxial parameters. These preliminary tasks are helpful for structure design of devices and growth condition control. In addition to the studies of SAG techniques, Ohmic contact characteristics of metals onto the GaN template substrates after removing SiO2 mask layers is also discussed. Commercial GaN-based LEDs are grown on insulating sapphire substrate. The device fabrication needs a dry etching procedure to define the active region of devices. The SAG technique leaves out the dry etching procedure. The selectively grown GaN-based LEDs with obliquely self-assembled facets improve the probability of photons to escape from semiconductors to air. Furthermore, a concave top surface was observed in a GaN-based LED when the epitaxial growth was performed by the aforesaid SAG technique. The concave top surface is beneficial to current spreading compared with those GaN/sapphire-based LEDs with planar top surface. For AlGaN-based p-i-n UV PD applications, the AlGaN heteroepitaxial layers grown on GaN template substrates with SiO2 mask layers (i.e., SAG technique) could have an effect that cracks in the AlGaN epitaxial layers could be markedly decreased compared with AlGaN epitaxial layers grown on conventional GaN template substrates. To further improve the responsivity of a conventional ultraviolet p-i-n photodiode, a wide bandgap and low-resisitivity p-type AlGaN top contact layer is necessary. In this study, an inverted AlGaN-based p-i-n photodiode, which the low-resistivity n-type AlGaN was served as the top contact layer and the anode electrode was directly formed on the bottom p-GaN template layer, was performed by the SAG technique. All selectively grown AlGaN-based p-i-n photodiodes exhibit typical UV-to-visible spectral rejection ratio over three orders of magnitude. The inverted type of p-i-n UV PDs can have greater potential in achieving solar-blind AlGaN/GaN-based p-i-n PDs with high aluminum content. This is because the top window layer will be an n-type AlGaN layer rather than a high resistivity p-type layer.

摘要 I
Abstract II
Contents IV
Table Captions VI
Figure Captions VII
CHAPTER 1 Introduction 1
1.1 Group III-Nitride Compound Semiconductors: Properties ＆ Applications 1
1.2 Background of Group III-Nitride Semiconductors 5
References in chapter 1 11
CHAPTER 2 Metalorganic Vapor Phase Epitaxy System 19
2.1 Introduction 19
2.2 MOVPE System 22
2.3 In-situ Monitoring of Growth Technology 23
References in chapter 2 28
CHAPTER 3 Selective Growth of GaN and AlxGa1-xN on GaN Template Substrates by Metalorganic Vapor Phase Epitaxy 30
3.1 Introduction 30
3.2 Growth and Characterization of GaN Grown by Selective MOVPE 31
3.3 Growth and Characterization of AlxGa1-xN Grown by Selective MOVPE 51
References in chapter 3 58
CHAPTER 4 Effects of Thermal Annealing on Si-Doped GaN and Mg-Doped GaN Epilayers with SiO2 Passivation Layers 62
4.1 Introduction 62
4.2 Study of Cr/Au Contacts on MOVPE-annealed N-type GaN Epilayers 64
4.3 Study of Ni/Au Contacts on MOVPE-annealed P-type GaN Epilayers 69
References in chapter 4 75
CHAPTER 5 GaN-based Light Emitting Diodes Grown by Selective Metalorganic Vapor Phase Epitaxy 77
5.1 Introduction 77
5.2 Growth and fabrication of selectively grown GaN-based LEDs 79
5.3 Characterization of selectively grown GaN-based LEDs 80
5.4 Power chip of Selectively Grown GaN-based LEDs 91
References in chapter 5 96
CHAPTER 6 AlGaN/GaN-Based Ultraviolet p-i-n Photodiodes 99
6.1 Introduction 99
6.2 Selective growth of Al0.25Ga0.75N/GaN Ultraviolet p-i-n Photodiodes 103
6.3 Inverted Al0.25Ga0.75N/GaN Ultraviolet p-i-n Photodiodes Formed on p-GaN Template Layer 112
6.4 Comparison of GaN-Based Ultraviolet p-i-n Photodiodes with Top p-Layer and Inverted p-Layer Structure 121
6.5 Inverted Al0.45Ga0.55N/GaN Solar-Blind p-i-n Photodiodes Formed on p-GaN Template Substrate 130
References in chapter 6 140
CHAPTER 7 Conclusions and Future Works 145
7.1 Conclusions 145
7.2 Future Works 147
Publication List 148
Appendix Characterization of Gallium-doped Zinc Oxide Contact on n-type Gallium Nitride Epilayers and Application to Ultraviolet Photodectector 150
References in appendix 175

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