臺灣博碩士論文加值系統

摘要
發光二極體（Light Emitting Diode；LED）是一種可發光的半導體元件，發光二極體具有體積小、消耗功率低、使用壽命長等特性。其發展的過程經歷了試圖尋找出更好的發光材料、如何使電流分布更均勻等。大致上看來，如今的發光二極體架構已無太大的變化，可是高亮度的發光二極體應用越來越廣泛，因此開始針對如何增加其發光效率就變的更加重要。
由於磊晶成長技術的成熟及相關製程的改善使得以氮化鎵做為基材的發光二極體，量子效率大幅地提升。然而，和以砷化鎵做為基材的發光二極體比較起來，在外部量子效率方面，它還是顯得不足。其中一個原因可能是電流非均勻分佈的關係，另外一個原因則是因為半導體材料高折射係數及半導體裡一些缺陷的緣故導致光不容易發射至外界而被半導體本身所吸收。
在發光二極體的正面，由於氮化鎵的折射率（約2.4）和空氣的折射率（1）差異相差很大，所以光經過折射率差異大的介質時，光穿透的比例將會減少，造成在介面上會部分的光會折射回來造成光的損失，因此我們用二氧化矽這用來做為發光二極體的抗反射層（Antireflective Films），並根據理論上薄膜干涉的計算及模擬，找出建設性干涉的膜厚，以提昇發光二極體的發光強度，並對沒有鍍抗反射層的發光二極體作光強度上的比較；其次，再以表面粗糙化以減少菲涅爾損耗（Fresnel Loss）的理論根據，在光學鍍膜的表面進行再進一步的微米陣列處理，採用了三種微米孔洞陣列結構的排列方式，包含三角孔洞陣列結構、矩形孔洞陣列結構以及六角孔洞陣列結構，進一步的提升提昇發光二極體的發光強度。

Abstract
LED one semiconductor component that can luminesce, it is small, consuming power low and having long performance life etc. It seems that structure of LED of today has not had too great change yet. But high efficiency LED uses more and more extensive, so the one that begin to how to increase efficiency is more important.
Because of improved epitaxial growth and advanced process technology, the quantum efficiencies of GaN-based LEDs are increased. However, the external quantum efficiencies are less significantly than that based on GaAs. One of the reasons is that non-uniform current spreading and the other is that light could be re-absorbed by material as a result of the high refractive indices of semiconductor materials and defects.
On topside of LEDs, the difference of refractive index between GaN (about 2.4) and air (1) is large, so the percentage of transmission is lowered. SiO2 is coated on the topside of InxGa1-xN/GaN LEDs as passivation and/or antireflective layer. According to the theory of interference, it can be suggest that the thickness of thin film with constructive interference will achieve the purpose of improving emissive intensity. And the intensity of LEDs coated with passivation and/or antireflective layer compared with that of non-coated LEDs will be discussed.
Secondly, used surface roughness to reduce Fresnel Loss. On topside of optical coatings go on further deal with micron hole array. Permutation way to adopt three kinds of hole array structure. Include triangular hole array structure, rectangle hole array structure and honeycomb hole array structure. Further improvement promotes the luminous intensity of LED.

目　錄
誌謝.......................................................i
中文摘要..................................................ii
英文摘要..................................................iv
目錄......................................................vi
第一章　序論...............................................1
1-1 藍光發光二極體分類..................................1
1-2 氮化鎵材料的發展簡史................................4
1-3 氮化鎵發光二極體的應用..............................8
1-4 光子晶體的發展簡介..................................9

第二章　發光二極體的概述與光學增益的理論探討..............18
2-1 氮化鎵發光二極體...................................18
2-1.1 能帶形成的原因.................................18
2-1.2 直接能隙與間接能隙.............................20
2-1.3 氮化鎵材料概述.................................22
2-1.4 氮化鎵系列的N 型與P 型摻雜....................23
2-1.5 發光二極體工作原理與發光機制...................24
2-1.6 雙異質接面結構可提高發光效率...................29
2-2 發光二極體表面處理之光學增益.......................30
2-2.1 光學損耗的理論介紹.............................32
2-2.2 發光二極體表面抗反射層結構.....................37
2-2.3 發光二極體表面增加結構.........................43

第三章　實驗樣品、製程與儀器介紹...........................49
3-1 實驗樣品結構與製程.................................49
3-1.1 實驗樣品結構...................................49
3-1.2 抗反射層結構製程...............................50
3-1.3 表面孔洞陣列結構製程...........................51
3-2 光激螢光光譜儀.....................................57
3-2.1 光激螢光光譜儀的原理...........................57
3-2.2 光激螢光光譜儀裝置.............................61
3-3 光譜儀.............................................65
3-3.1 光譜儀的介紹...................................65
3-3.2 光譜儀的構造...................................66
3-3.3 光譜儀的運作方式...............................67
3-4 掃描式電子顯微鏡...................................68
3-4.1 掃描式電子顯微鏡原理...........................68
3-4.2 掃描式電子顯微鏡應用...........................68
3-5 原子力顯微鏡.......................................71

第四章　實驗結果與討論....................................74
4-1 InGaN/GaN 樣品光學特性分析........................74
4-2 單一多層膜結構的抗反射層之光學增益.................76
4-3 表面孔洞陣列結構之光學增益.........................83
4-4 有效折射率（Effective-Index）的理論分析與模擬..........89
4-5 矩形孔洞陣列結構之光學特性分析....................97

第五章　結論.............................................104

第六章　未來展望.........................................106

參考文獻.................................................108

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