Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/48611
標題: Effects of Surface Morphologies of Array Roughening on the Characteristcs of Light Emitting Diodes
週期性粗化之表面形貌對發光二極體特性影響之研究
作者: 洪瑞華
關鍵字: 應用研究
Light Emitting Diodes (LEDs)
光電工程
發光二極體
週期性陣列表面粗化
隨機分佈表面粗化
反射鏡面基板
氧化鋅
奈米線
array roughening surface
random rougheningsurface
mirror substrate
ZnO
narowires
摘要: In conventional LEDs, the external efficiency is limited by the total internal reflection inthe semiconductor–air interface because of the different refractive indices between thesemiconductor and air. Thus, the internal light has difficulty in escaping into the air from thesemiconductor. The total light reflection effect on the light extraction efficiency for the LEDswith large areas (1 mm×1 mm) is more obvious as compared to that of the LEDs with smallareas (0.3 mm× 0.3 mm). Because the LED structure is a lateral waveguide, it results inincreasing the probability of reabsorption. For most conventional LED』s, the externalefficiency is limited by total internal reflection of the generated light from active layer, whichoccurs at the semiconductor-air interface. This is due to the difference in the refractive indexbetween semiconductor and air. There are two methods have been implemented to increasethe luminous efficiency. One is via changing the shape of LED-chip to geometry, another isvia surface texturing. Recently, it has been shown that random roughening the LED surfacecan increase the light extraction efficiency of the nitride-based LEDs. The textured surfaceswere obtained by using plasma etching directly on the top epilayer or top ITO layer by naturallithography or wet etching the n-type GaN layer. Up to now, there is no systematically tocompare the effect of random or array surface roughening on the light extraction quantumefficiency.In this project, the mass-product technique of the array surface roughening for p-typeGaN (first year, etching) or n-type GaN (second year, etching) with sapphire, mirror/Si ormirror/Cu substrate will be developed. The third year, the array roughening will be obtainedby growing the ZnO narowire on the p-type GaN layer with flat surface or roughening surface(by low-temperature growing GaN). The ZnO narowires will also be grown on the thin n-typeGaN epilayer to fabricate the roughening surface thin GaN LEDs. We hope that the dimensionand the surface roughening states (random or array/ etching or growing up) can be establishedfor the high external quantum efficiency LEDs applications.
傳統發光二極體(LED)因本身具有低熱傳導之特性,所以發光效率一直無法提升,更無法於高電流下操作,直到以晶片黏貼技術將具鏡面反射之高熱傳導基材取代傳統LED 的低熱導之基材,這樣是利用反射鏡面將向下發射的光反射至上方以達到發光效率的大幅提升,如此一來可解決基板吸光或基板散熱不良之問題。儘管如此,在發光二極體之結構仍存在因半導體折射率與空氣或其他封裝材料折射率的不同,而易形成光全反射之現象,而仍有部份光會全反射回發光區。特別是對大面積(1 mm×1 mm)之功率晶粒而言,此現象更為明顯。為了改善此因素對發光效率的影響,以表面粗化來減低光在發光二極體裡全反射的機率,這樣一來可再將發光效率大幅拉升。傳統之粗化是利用乾式蝕刻或濕式蝕刻對半導體表層進行隨機分佈之粗化表面,且至目前為止,尚未有系統討論粗化尺寸與表面形貌對LEDs 外部量子效率提升之影響。本計劃主要研究目的為利用週期性之表面粗化技術藉以提升 LED 外部量子效率。共分為三年,第一及二年是研發具量產型之週期性陣列粗化技術(蝕刻方式),藉由週期性陣列結構粗化p-GaN 與n-GaN 表面,進而探討此類粗化效果與傳統隨機型粗化效果對發光效率之影響,並且製作成具反射鏡面及高散熱基板之表面粗化高功率發光二極體。第三年是使用磊晶技術直接於氮化鎵系列之發光二極體磊晶片(此類磊晶片可以是磊晶於藍寶石基板, 或是移除藍寶石基板轉貼於矽基板或電鍍銅基板之磊晶膜)沈積出具粗化效果之氧化鋅奈米線。希望藉此研究對週期性或隨機性之LED 表面粗化,無論是蝕刻方式或長晶方式之粗化技術,提供一理論模型與製程技術,得以有效設計與製作表面粗化形貌,用以提升LEDs 外部量子效率。
URI: http://hdl.handle.net/11455/48611
其他識別: NSC96-2628-E006-260-MY3
文章連結: http://grbsearch.stpi.narl.org.tw/GRB/result.jsp?id=1618057&plan_no=NSC96-2628-E006-260-MY3&plan_year=97&projkey=PB9706-1465&target=plan&highStr=*&check=0&pnchDesc=%E9%80%B1%E6%9C%9F%E6%80%A7%E7%B2%97%E5%8C%96%E4%B9%8B%E8%A1%A8%E9%9D%A2%E5%BD%A2%E8%B2%8C%E5%B0%8D%E7%99%BC%E5%85%89%E4%BA%8C%E6%A5%B5%E9%AB%94%E7%89%B9%E6%80%A7%E5%BD%B1%E9%9F%BF%E4%B9%8B%E7%A0%94%E7%A9%B6
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