利用奈米圖案化藍寶石基板以增強氮化鎵發光二極體之光輸出功率

Abstract

近幾年來許多相關研究致力於氮化鎵發光二極體之發光效率的提升，由於氮化鎵主要成長於藍寶石基板上，兩者之間晶格常數和熱膨脹係數差異造成晶格不匹配，導致氮化鎵的磊晶品質降低，且材料本身擁有的極化現象會造成元件主動層發生量子侷限史塔克效應，進而使發光二極體的內部量子效率下降。為解決此問題，我們以實驗室搭載的電子束微影系統搭配濕式蝕刻技術製作出奈米大小之孔洞結構和柱狀結構圖案化藍寶石基板，並設計圖案直徑或間距大小以及改變蝕刻時間，且利用聚焦式離子束電子束顯微系統確認製作完成的藍寶石基板圖案是否正確。本論文主要欲探討氮化鎵成長在藍寶石基板上時，兩材料間之接面過渡層中氮化鎵與藍寶石基板所佔比例關係是否影響元件特性。

Recently, many studies have dedicated to the improvement of the efficiency of GaN-based light-emitting diode (LEDs). GaN-based LEDs are typically grown along the c-plane sapphire substrates. However, the difference between lattice constant and thermal expansion coefficient result in the lattice mismatch, which causes the reduction of the quality of GaN epilayer.In addition, the internal quantum efficiency will be degraded because of the lattice mismatch, induced related polarization filed, called quantum confined stark effect (QCSE). In order to overcome the problem, electron-beam lithography and wet-etching technology are used to achieve NPSSs with exact dimensions in the experiment. The air hexagonal arrays are fabricated on the c-plane sapphire substrate under different wet-etching conditions. The surface morphology, periodicity, depth, space, and diameter of accomplished NPSSs are re-examined with the instrument of FEI Dual-Beam NOVA 600i Focused Ion Beam. Next, the InGaN-based LED samples are grown on the NPSSs with an atmospheric-pressure metal organic chemical vapor deposition (AP-MOCVD) . To accomplish the accuracy of the measured data, the micro-photoluminescence (μ-PL) spectroscope is equipped with the C-Focus system, which corrects microscopefocus drift.