圖形化藍寶石基板應用於氮化鎵發光二極體之研究

A study of patterned sapphire substrates on GaN-based light-emitting diodes

張育嘉(Yu-Chia Chang)

指導教授 ： 張正陽

國立中央大學/理學院/光電科學研究所/碩士(2008年)

摘要

目前發光二極體在固態照明上的應用越來越廣，國內外有許多團隊利用圖樣化藍寶石基板來提升發光二極體的內部與外部量子效率。本論文最主要的目的為，使用化學濕式蝕刻法和乾式蝕刻法將微米結構圖樣製作於發光二極體的藍寶石基板(sapphire substrates)，藉此來改善發光二極體的光萃取與出光效率。
在化學濕式蝕刻法方面，利用高溫酸液，做出具有晶面圖樣的圓洞形藍寶石基板；在乾式蝕刻法方面，結合光阻熱融，雙重擋層，並利用導熱介質於藍寶石背部改善熱傳導，做出高度更大的半球形藍寶石基板。磊晶後得知圓洞狀圖樣藍寶石基板與氮化鎵之間會有空隙的產生，而半球形圖樣藍寶石基板則不會。
在電性上，圖樣化藍寶石基板發光二極體與傳統發光二極體的電流電壓曲線非常相似，電性沒有被破壞。在電制激發光譜上可看出，圖樣化藍寶石基板可以減少Fabry-Perot現象。以圓洞圖樣藍寶石基板製作之發光二極體，光輸出功率提升39％。以半球形圖樣藍寶石基板製作之發光二極體，圖樣週期為4.5µm、5.0µm、6.0µm時，其光輸出功率分別提升45％、36％、29％，與光萃取理論模擬結果34.6％、33.3％、31.3％，因此我們可以發現實驗與模擬方面在趨勢上是相當符合的。

關鍵字

圖形化藍寶石基板 ； 發光二極體

並列摘要

At present light-emitting diodes (LED) in the application of solid-state lighting is interested. Many teams use patterned sapphire substrates (PSS) to improve the internal and external quantum efficiency. The main purpose of this thesis is using of chemical wet-etching and dry-etching method to fabricate micro-PSS to improve the light extraction efficiency of LED.
For chemical wet-etching, a circular array composed to crystal face is fabricated by high temperature acid. For dry-etching, we made a deeper PSS structures by different hard masks such as photoresist reflow, double hard mask.
Electrical property of PSS LED is as same as conventional LED. PSS LED can reduce Fabry-Perot phenomenon under the EL measurement so that light output power improvement is 39% by wet-etching PSS process. An improvement of 45%、36%、29% on the output power was achieved by adopting the 4.5µm、5.0µm、6.0µm period of hemispherical PSS LED. The trend of actual light output power is closed to simulation result of light extraction efficiency.

並列關鍵字

PSS ； patterned sapphire substrates ； LED ； light-emitting diodes

參考文獻

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