- 學位論文
以背鍍分佈式布拉格反射鏡提升發光二極體發光效率之研究
Enhancing extraction efficiencies of light-emitting diodes with distributed bragg reflectors
摘要
近年來，利用寬能隙半導體 (Wide band gap semiconductor) 材料製造紅、黃、綠光發光二極體 (Light emitting diode, LED) 已經有很大的進展。一直到近年來，以InGaN/GaN為主的材料成功製出藍光LED，配合黃色螢光粉製造出白光LED，宣告了以白光LED 為照明主流的時代即將來臨。然而，為了未來的照明上的應用，進一步提升LED 的外部量子效率是非常重要的課題。 本論文主旨在於探討如何藉由在LED 晶片底部鍍上分佈式布拉格反射鏡的方式，來增進 LED 模組之光萃取效率(extraction efficiency)以及增進白光LED 模組的光學特性：主要利用TFCalc 軟體進行分佈式布拉格反射鏡之設計與模擬，再以TracePro 光學軟體進行整體LED 模組的設計與模擬，並輔以實際實驗量測結果來確認模擬結果的正確性與可靠性。 首先我們以TFCalc 軟體模擬不同形式之分佈式布拉格反射鏡，將其不同波長對不同入射角度之反射率設定至TracePro 之表面特性，搭配上由實驗量測或文獻上查得的其餘LED 模組的參數資料，建立了此種LED 封裝模組的模擬模型，便可藉由TracePro 軟體模擬推測各種不同尺寸LED 晶片封裝模組之光學特性及加鍍反射鏡對其發光效率之影響，再以實作的方式，將所設計之反射鏡鍍於LED 晶片底部，再進行封裝以及相關特性之量測。 加鍍反射鏡對於尺寸越大之LED 晶片封裝模組，其對光萃取效率之增加更為明顯，13 mil-13mil之LED 晶片其發光強度增益為9.65%，而45 mil-45 mil之LED 晶片其發光強度增益則遽增至31.85%，將LED 晶片拋光後鍍上反射鏡為未來提升LED 封裝模組光萃取效率方法之一。
並列摘要
Recently, wide-band-gap semiconductors have been attracting great interest for applications to optoelectronic devices such as light-emitting diodes (LEDs). For last few years, InGaN/GaN-based blue light-emitting diodes (LEDs) have been successfully fabricated and following comes the epochal of white light LED.However, for future illumination applications, it is a very important topic to further enhance the external quantum efficiency of LEDs. In this thesis, we deposited the distributed bragg reflector on the backside of LED chips to improve the extraction efficiency and light characteristic of a white light LED module. First, the optical software TFCalc was used to design the distributed bragg reflector. And the optical software TracePro was used to design the LED module. We finally compared the simulation result with the actual experiment result. We used the optical software TFCalc to design different DBR structures. Then we set the reflectivity of the optimized DBR structure to the surface property of TracePro. We established the simulation model by TracePro software for the white light LED using a blue LED chip with YAG:Ce phosphor. We could simulate how the extraction efficiency of LED model was enhanced by the DBR. The designed DBR was deposited on the backside of LED chips which were packaged and measured. Depositing DBR on the backside of LED chips was more helpful for enhancing the extraction efficiency of bigger LED chip size. The light output power enhancement of 13 mil-13 mil LED chip was 9.65%, but that was 31.85% for the 45mil-45 mil LED chip. Depositing DBR on the backside of LED chips was one of the ways to enhance the extraction efficiency of LED model.