以二氧化矽奈米粒子改善氮化鎵發光二極體發光效率之研究

Abstract

在氮化鎵發光二極體上製作表面粗化、表面結構、或光子晶體等來提升發光二極體之外部量子效率，一直都是很多團隊研究的目標。本文中提出一種自組成單層奈米粒子遮罩搭配ICP-RIE乾式蝕刻的製程方法在氮化鎵元件上面製作奈米級的表面結構，討論其對發光效率提升情形，並考慮不同尺寸奈米結構對發光效率的影響，藉此歸納出提升發光效率的設計方向。另外，在發光二極體元件上製作透明導電層ITO來增加電流傳導擴散為目前業界很普遍的情形，本文亦嘗試在透明導電層ITO上製作表面奈米結構，並探討其對發光效率的提升情形。 一維的氮化鎵半導體材料奈米結構，如奈米柱、奈米線、奈米管等，不管在基礎物理研究或新科技應用上更是被寄予高的期望。本文採用由上而下製程(Top-down process)來製備高密度、高均勻性的氮化銦鎵/氮化鎵多重量子井奈米柱發光二極體，量測其光激發光頻譜(PL)，發現此種高密度、高均勻性的氮化銦鎵/氮化鎵多重量子井奈米柱發光二極體有一個相當寬頻帶的黃放光(yellow luminescence)現象。

In this paper, we present a novel method to fabricate textured GaN-based LEDs using a SiO2 nano-mask and ICP dry etching. The SiO2 nano-particles are placed on top of the p-type layer simply by spin-coating or immersion. The optical output power of a surface textured LED is 1.4 times higher than that of a conventional LED (a LED without surface textured). In addition, the current-voltage (I-V) curve of the textured LED is nearly the same as that of a conventional LED, which implies that the fabrication process greatly improves light extraction efficiency without damaging the electrical properties of the LED material. One-dimensional nanostructures, such as nanotubes, nanowires, and nanorods, of GaN-based nitride semiconductors are known to have great prospects in fundamental physics and novel technological applications. However, fabrication and characterization of well-ordered nanostructures with high density are very important for the practical device applications. In this paper, we present InGaN/GaN MQW nanorod LEDs. From photoluminescence measurements, we observed a blue shift of the peak wavelength and a broad band yellow luminescence in the nanorod LED samples.