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系統識別號 U0026-2207201323323700
論文名稱(中文) 改良型垂直導通氮化鎵發光二極體之研製及特性改善與分析
論文名稱(英文) Fabrication and Characterization of Advanced Vertical-type GaN-based Light-emitting Diodes
校院名稱 成功大學
系所名稱(中) 光電科學與工程學系
系所名稱(英) Department of Photonics
學年度 101
學期 2
出版年 102
研究生(中文) 楊於錚
研究生(英文) Yu-Chen Yang
學號 l78971013
學位類別 博士
語文別 英文
論文頁數 127頁
口試委員 指導教授-許進恭
召集委員-張守進
口試委員-賴韋志
口試委員-李允立
口試委員-林恆光
口試委員-洪瑞華
口試委員-杜立偉
口試委員-郭浩中
口試委員-郭政達
中文關鍵字 發光二極體  氮化鎵  藍寶石基板  垂直式 
英文關鍵字 Light-emitting Diode  GaN  Sapphire substrate  Vertical type 
學科別分類
中文摘要 近年來因應節能風潮,發光二極體的應用已從傳統的指示燈逐漸轉換至背光光源、戶外看板及室內外照明等領域。新的應用範圍所需供應的亮度較高,因此驅動每一顆發光二極體所使用的電流及其輸出的瓦數也較高,實際使用狀態下產生的熱能如何散逸也就成為了一個十分重要的課題。常見的改良方式是選擇將散熱較差的藍寶石基板置換成其他導熱係數較佳的材料作為新的基板,但因使用基板剝離技術容易導致磊晶應力釋放,可能導致漏電流的產生。本論文主要針對垂直導通型的發光二極體之光電特性進行改善,第一部分將會先討論如何改善固有製程中已知的問題點。第二部分我們就光電特性的提升,在此結構上捨棄將藍寶石基板移除的製程,改由研磨及蝕刻製程將n型氮化鎵暴露出來,並保留部分的藍寶石原生基板,不僅可避免因使用基板剝離技術而造成的漏電流,且發光效率還可進一步提升。最後我們因應未來照明趨勢可能會偏向高電壓及高功率操作,設計一款高壓串接式的發光二極體。此種設計組合了數個發光二極體單元於單一基板上,因每一發光二極體單元的尺寸較小,因此電流分布較佳,同時也觀察到個別晶粒均有操作電壓降低及發光效率提升之現象,結合散熱能力佳及高發光效率兩大優勢,更適合作為新一代高功率應用的元件。
英文摘要 In recent years, the applications of light-emitting diodes (LEDs) gradually transit from traditional indicator lamps to backlighting, outdoor billboards, and lighting. New applications need higher brightness, and the input power for these applications is also increased. How to dissipate the heat out from LEDs has become a very important issue. One solution is to use new materials with high coefficient of thermal conductivities to replace the sapphire substrate. But the strain release and laser-induced damage on the GaN-based epitaxial layers led to the degradation of electrical properties of the conventional vertical LEDs. In this dissertation, we will research how to improve the optical and electrical characteristics of vertical InGaN LEDs. The first part focuses on the process improving on vertical InGaN LEDs. The design of the Vertical InGaN LEDs with a retained sapphire will be discussed at the second part. This design can reduce the reverse leakage current (Ir) because there are no strain release and laser-induced damage on the GaN-based epitaxial layers. Also, the top sapphire layer serves as a window layer to facilitate light extraction. At last section, we propose designs of high voltage vertical InGaN LEDs. These designs connect several LED cells on a single substrate in series or parallel. Because the LED cells are smaller than regular ones, they have more uniform distribution of injection current. The characteristics of forward voltages and light extraction efficiencies of high voltage vertical InGaN LEDs are also better than vertical InGaN LEDs with single cell. The multi-cell vertical InGaN LEDs are more suitable for high power applications in the future.
論文目次 摘要……………………………………………………………………………………………………………………………………………… I
Abstract……………………………………………………………………………………………………………………………………II
致謝………………………………………………………………………………………………………………………………………… III
Contents………………………………………………………………………………………………………………………………… IV
Table Captions……………………………………………………………………………………………………………… VII
Figure Captions………………………………………………………………………………………………………… VIII
Chapter 1 Introduction…………………………………………………………………………………………… 1
1.1 Recent development of high power InGaN light-emitting diodes………………………………………………………………………………………………………………… 1
1.2 The advantage of vertical InGaN light-emitting diodes………………………………………………………………………………………………………………………………………… 3
1.3 Motivation…………………………………………………………………………………………………… 11
References in Chapter 1………………………………………………………………………………………… 12

Chapter 2 Process improving on vertical InGaN light-emitting diodes……………………………………………………………………………………………………………… 14
2.1 The high reflectivity Ohmic contact layer on p-GaN…… 14
2.2 The barrier layer on Ag layer…………………………………………………………… 20
2.3 The encapsulated reflector…………………………………………………………………… 25
2.4 The void-free wafer bonding process…………………………………………… 31
2.4.1 The preparation of samples……………………………………………………………… 32
2.4.2 Results and discussion………………………………………………………………………… 33
References in Chapter 2………………………………………………………………………………………… 40

Chapter 3 Vertical InGaN light-emitting diodes with a sapphire-face-up structure………………………………………………………………………………… 41
3.1 Introduction………………………………………………………………………………………………………… 41
3.2 The preparation of samples…………………………………………………………………… 46
3.3 The retained sapphire substrate……………………………………………………… 49
3.3.1 Sapphire thinning by grinding and polishing………………… 49
3.3.2 Sapphire etching by inductively coupled plasma (ICP)……………………………………………………………………………………………………………………………………………………… 51
3.4 Comparison of optical and electrical characteristics between VLEDs with and without retained sapphire……………………… 59
3.5 Sapphire surface texturing…………………………………………………………………… 69
3.5.1 Formation of metal nanomask…………………………………………………………… 69
3.5.2 Sapphire surface texturing by ICP dry etching…………… 70
3.6 The VLEDs with retained patterned sapphire substrate……………………………………………………………………………………………………………………………… 77
3.6.1 The morphology of exposed GaN layer……………………………………… 77
3.7 Comparison of optical and electrical characteristics between VLEDs with and without retained patterned sapphire………………………………………………………………………………………………………………………………… 81
3.8 The light output efficiency simulation for difference sapphire thickness……………………………………………………………………………………………………… 90
3.9 Comparison between vertical InGaN light-emitting diodes with retained patterned sapphire and the flip-type InGaN light-emitting diodes……………………………………………………………………………………………… 95
3.9.1 The conventional InGaN flip-chip……………………………………………… 95
3.9.2 The advanced InGaN flip-chip………………………………………………………… 96
3.10 Results and discussion………………………………………………………………………… 102
References in Chapter 3……………………………………………………………………………………… 103

Chapter 4 The multi-cell vertical InGaN light-emitting diodes…………………………………………………………………………………………………………………………………… 107
4.1 The efficiency improving limitations on vertical single-cell InGaN light-emitting diodes…………………………………………… 107
4.2 High voltage design of vertical multi-cell InGaN light-emitting diodes…………………………………………………………………………………………………………… 108
4.3 The preparation of samples………………………………………………………………… 111
4.4 Comparison of optical and electrical characteristics between single-cell and multi-cell VLEDs………………………………………… 115
4.4.1 Current spreading analysis with near field measurement……………………………………………………………………………………………………………………… 116
4.5 Results and discussion…………………………………………………………………………… 123
References in Chapter 4……………………………………………………………………………………… 124

Chapter 5 Conclusions and future works…………………………………………… 125
5.1 Conclusions………………………………………………………………………………………………………… 125
5.2 Future works……………………………………………………………………………………………………… 126

Publication List………………………………………………………………………………………………………… 127

參考文獻 References in Chapter 1
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References in Chapter 2
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References in Chapter 3
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References in Chapter 4
[1] A. Keppens, W. R. Ryckaert, G. Deconinck, and P. Hanselaer, “High power light-emitting diode junction temperature determination from current–voltage characteristics,” J. Appl. Phys., vol. 104, 093104, 2008.
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