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Title: | 研究與發展發光二極體特性之即時非破壞檢測技術 R&D of Real-Time Non-Destructive Characterization Methods for Light Emitting Diodes |
Authors: | Pei-Ting Chou 周佩廷 |
Advisor: | 李世光 |
Keyword: | 發光二極體,即時晶圓曲率監控,低頻雜訊頻譜,矽光電二極體感測器,光度量測, light-emitting diodes,in-situ curvature monitoring,low-frequency noise spectrum,silicon photodiode,photometric measurement, |
Publication Year : | 2016 |
Degree: | 博士 |
Abstract: | 近年來,以氮化鎵材料為基礎之發光二極體(LEDs),特別是紫外光發光二極體(UV LEDs),由於其具有作為照明光源與殺菌、生醫等多種應用,因此受到注目,如何判斷其品質與可靠度也成為相當重要的議題。目前對於發光二極體晶粒生產廠商而言,晶粒的各項光電特性皆可經由磊晶與製程技術加以改變及控制。而發光二極體光源所產生的光通量大小對於照明或燈具製造商而言是最重要的參數之一。
本論文針對發光二極體,特別是紫外光發光二極體從上游磊晶製造至下游封裝應用,改良並提出四種評估其特性之檢測方法,以利於提升品質可靠度:1.磊晶成長之即時晶圓曲率監控,2.以低頻雜訊頻譜評估氮化銦鎵發光二極體之可靠度,3.以大面積矽光電二極體感測器(silicon photodiode)進行發光二極體晶粒之光度量測,4.以矽光電二極體感測器組合箱(assembled box of Si photodiodes)進行發光二極體之部分光通量測量。 在晶粒品質檢測方法部份,由於目前市售晶粒大都成長在藍寶石、碳化矽或矽等高度晶格不匹配的基板上,而晶格不匹配會造成磊晶基板的彎曲或破裂以及缺陷密度的大幅提升,因此磊晶過程中的基板曲率變化及磊晶完成後晶粒缺陷情形的量測一直以來都是氮化鎵發光二極體的重點。因此,建立磊晶曲率變化監控技術並深入分析不同型態的缺陷密度對於未來提升LED發光效率及增加可靠度更顯得重要。本研究即以磊晶成長之即時晶圓曲率監控及低頻雜訊頻譜評估氮化銦鎵發光二極體之可靠度,其中晶圓曲率監控包含以兩雷射光點距離、線雷射長度、兩平行雷射距離等三種方式來評估曲率變化情形。在缺陷密度評估方面以低頻雜訊頻譜量測與X光繞射(XRD)缺陷密度量測的結果進行比對。 在光通量量測部份,目前多以全光通量或部分光通量的積分球量測架構為主,但部分光通量的積分球量測有開口收光面積較小問題,且針對紫外光發光二極體而言,紫外光光源會嚴重損壞積分球的硫酸鋇(BaSO4)塗層,使得積分球無法長期使用,本研究開發以矽光電二極體為收光單元解決上述的問題,內容包含以大面積矽光電二極體感測器(silicon photodiode)進行發光二極體晶粒之光度量測及以矽光電二極體感測器組合箱(assembled box of Si photodiodes)進行發光二極體之部分光通量測量。於不同量測架構的設計,藉由光學模擬與實驗以驗證量測結果。 In recent years, gallium nitride (GaN) based light-emitting diodes, especially ultraviolet light-emitting diodes (UV LEDs) have been attracted much interest for several applications and purposes, with the rapid development and extensive use of UV LEDs, evaluating their quality and reliability is very important. For LED manufacturers, the optoelectronic characteristics of LED chips can be altered and controlled through adjusting epitaxial and process technology, and the quantity of luminous flux from LEDs is one of the most important parameters to lighting and luminaire manufacturers. This thesis studies four detection methods for improving the quality and reliability of LEDs, which are 1. monitoring the curvature of the LED wafer during the growth process, 2. analysis of the reliability of the Indium Gallium Nitride (InGaN) LED using the low-frequency noise spectrum, 3. photometric measurement of LED chips using a large-area silicon photodiode and 4. photometric measurement of the partial radiant flux of the LED using an assembled box of Si photodiodes. In the quality testing methods of LED chips, the measurements of LED wafer curvature and chip defect density are the critical issues. It is due to most commercial LED chips are grown on a substrate with a high lattice mismatch such as sapphire, silicon carbide and silicon, which may cause epitaxial substrate bending or crack, and largely increased dislocation density. Therefore, it is important to develop in-situ wafer curvature monitoring technology and further analyze different types of defect densities to enhance the luminous efficiency and reliability of LEDs. In this thesis, the reliability of InGaN LEDs was evaluated through monitoring the curvature of the LED wafer during the growth process and analyze low-frequency noise spectrum. Three measurement methods such as the distance between two circular laser spots, the length of a single line laser, and the vertical distance between the two parallel laser lines can be used to evaluate the curvature. The low-frequency noise spectra were measured and the defect density was compared with that calculated by XRD measurement. It is common using an integrating sphere to measure the total or partial luminous flux of LEDs, however, the small opening of an integrating sphere during partial flux may influence the measurement result. For UV LEDs, the BaSO4 coating layer of integrating sphere may be damaged by UV light and cannot stand prolonged exposure to the UV spectrum. In this thesis, a large-area Si photodiode was used to evaluate the output power of LED chips, and the assembling Si photodiodes box method are used to measure the output optical power of a UV LED. Optical simulations and experiments were performed through various measurement configurations to verify the measurement results. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/19644 |
Fulltext Rights: | 未授權 |
Appears in Collections: | 工程科學及海洋工程學系 |
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