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標題: | 氮化鎵奈米柱發光二極體其應力與缺陷相依性之內部量子效率之特性探討 Characterization of Strain and Defect Dependent Internal Quantum Efficiency of InGaN/GaN Nanorod Light Emitting Diode Arrays |
作者: | Li-Chuan Huang 黃莉琄 |
指導教授: | 黃建璋 |
關鍵字: | 氮化鎵,奈米柱,發光二極體,內部量子效率,外部量子效率,光萃取效率,應力釋放,化學機械研磨, GaN,nanorod,light emitting diode,internal quantum efficiency,external quantum efficiency,light extraction efficiency,strain relaxation,chemical mechanical polishing, |
出版年 : | 2012 |
學位: | 碩士 |
摘要: | 近年來,由於氮化鎵其良好的特性,被廣泛的應用於短波長的發光元件。目前有許多研究團隊提出各式各樣的奈米結構技術來提升效率,而其中又以奈米柱發光二極體最受矚目。在本篇論文中,我們提出一種具實用價值之奈米小球微影術用以製作具有p-i-n結構之奈米柱陣列發光二極體元件並分析其特性,亦藉由拉曼量測證實奈米柱元件可有效地釋放發光層間的壓縮應力。
目前在一般的研究上,常用來定義發光二極體內部量子效率的方法主要是做低溫光致發光(photoluminescence)量測,通常假設當環境溫度非常低(接近0K)的時候,進行非輻射復合的載子數量會趨近於零,幾乎全部的載子都會進行輻射複合,因此定義此時的內部量子效率為100%。但是在我們低溫光致發光、低溫電致發光(electroluminescence)及低溫拉曼量測結果中發現,當溫度逐漸下降,每個元件缺陷逐漸被排除同時卻也伴隨著承受比室溫下更多的壓縮應力,因此我們提出了一個嶄新的模組來分析內部量子效率,此法不同於以往對於低溫的光致發光結果只歸因於缺陷的抑制,更將低溫下應力的因素一併考慮,故此法可幫助我們求出比以往更精確的內部量子效率。最後,藉由電致發光得到各元件的外部量子效率,進而可求得各元件的光萃取效率,進而從幾何觀點來探討奈米柱結構的貢獻。 在本論文中,我們藉由奈米柱元件與平面結構元件的應力及缺陷的差異,讓我們對發光二極體的效率探討有了新的思維,此一連串緊扣的複雜關係,將在本論文中一一剖析及呈現。 Recently, GaN has been widely applied to short-wavelength optical devices due to its superior optical and electrical characteristics. The InGaN/GaN nanorod light-emitting-diode array is one of the most popular structures. In this thesis, we demonstrated a practical approach to fabricate nanorod LED arrays. By means of the nanosphere lithography, the fabricated device has been proved to relax the compressive strain underneath the active layers effectively. Nowadays, a commonly employed method to find internal quantum efficiency (IQE) of a LED is by assuming complete frozen of defects at very low temperature and thus the IQE to be 100% as the injected carriers are all contributed to radiative recombination. Despite the simplicity, the method underestimates other factors for IQE. According to our temperature-dependent EL, PL and Raman measurement, we explored a severer strain effect accompanying the eliminating defects with decreasing temperature. Thus, we proposed a model to view the issue of IQE from a brand-new perspective. Taking both defects and strain into consider, it provides a way to figure out the more precise value of IQE than before. At last, we further discussed the external quantum efficiency and the light extraction efficiency on planar and nanorod LEDs. The comprehensive thinking of the optical efficiency on the planar and nanorod LEDs will be presented in this thesis. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/62659 |
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顯示於系所單位: | 光電工程學研究所 |
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