具表面次微米光柵氮化鎵發光二極體遠場光型調制之研究; Far-field Light Pattern Modulation of GaN-based LED with Sub-micron Grating

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题名:	具表面次微米光柵氮化鎵發光二極體遠場光型調制之研究;Far-field Light Pattern Modulation of GaN-based LED with Sub-micron Grating
作者:	朱健安;Chien-an Chu
贡献者:	光電科學研究所
关键词:	遠場光型;次微米光柵;發光二極體;sub-micron grating;light emitting diodes;far-field light pattern
日期:	2010-07-15
上传时间:	2010-12-08 14:20:49 (UTC+8)
出版者:	國立中央大學
摘要:	發光二極體雖具備眾多優點如體積小、壽命長及可靠度佳等優點，但一般未做處理之平板結構晶片，其光強度空間分布呈現朗勃遜光型，使光強度與收光角之間是餘弦遞減的關係。在此光型下LED為一指向性不良且出光均勻度差之光源。為優化LED之光型，本論文採用電子束微影及乾蝕刻技術並將其應用至LED晶片製程，在這樣的技術整合下，可以將次微米等級之一維光柵結構製作於LED晶片表面並以此達到光型調制的效果。透過發射光子與一維光柵結構之交互作用，除了能增加LED的光萃取效率外更可以達到光型調制的效果。本論文設計了週期為0.3 μm、0.5 μm、0.75 μm、1.0 μm與2.0 μm之光柵結構，並於兩種發光機制：光激螢光 (PL) 與電致發光 (EL) 下進行發光強度之角度解析量測。量測結果顯示週期的大小會影響發光光型的表現，在PL量測中週期0.5 μm之光柵可強化出光角度位在±25度之強度分佈，而週期2.0 μm之光柵則能均勻化出光角度介於±60度角間之強度分佈，EL之量測結果與PL相仿。此外為釐清受激放射與自發性複合的發光機制對光型調制的影響，本論文同時參考FDTD的數值模擬方法，就上述之發光機制結合光柵結構所提供的散射與繞射現象為切入點，來探討週期大小對遠場光型的影響並對實驗量測結果進行機制解釋。 Light emitting diodes (LEDs) have various advantages such as small size, long life and good reliability. However, the light intensity distribution of native planar LED chips performed a Lambertian light pattern in spatial distribution. It caused the light intensity decay with viewing angle by cosine law. When LED emitting far-field pattern in the Lambertian formation, it became a weakly directional and non-uniform light source. In this thesis, we modulated the light pattern of LED chip, by the e-beam lithography and the dry etching processes integrated with LED chip process. Under this process integration, the 1-D sub-micron grating was fabricated on the chip surface to achieve the modulation of LEDs chip light pattern. The light extraction enhancement was increased by the interaction between the emitting photon and the 1-D grating structure and the light pattern was also modulated. Five different periods of 1-D grating were designed (0.3 μm, 0.5 μm, 0.75 μm, 1.0 μm and 2.0 μm), and the angle-resolved measurements were completed under two luminescence mechanisms: the photoluminescence (PL) and the electroluminescence (EL).The results showed that the size of grating period affected the light patterns transition. In PL measurement, the grating period with 0.5μm, enhanced the light intensity at the observing angle of ±25°; the grating period with 2.0 μm, performed a light intensity in uniform between the observing angle of ±60°. The results of EL measurement were similar to that of PL. Furthermore, the effects of stimulated emission and spontaneous carrier recombination light pattern were evaluated by the FDTD analysis. The simulation results combined with different luminescence cases and the optics phenomenon resulted from the 1-D grating such as the scatter and the diffraction were used to discuss the relationship between the size of 1-D grating period, the far-field light patterns.
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