使用紅/綠螢光粉之白光發光二極體與具圖案藍寶石基板之發光二極體光學模擬之研究

A The Study of White LEDs with Red/Green Phosphors and Optical Simulation of LEDs with Patterned Sapphire Substrate

謝景翔(Ching-Hsiang Hsieh)

指導教授 ： 林俊良

崑山科技大學/工程學院/電子工程研究所/碩士(2008年)

https://doi.org/10.6828/KSU.2008.00019

摘要

發光二極體用於照明必須提昇其發光效率，為了提高發光二極體的發光效率最常見的方法是將晶粒上的發光側邊作表面粗化或是對藍寶石基板進行表面蝕刻，而圖形化藍寶石基板是在磊晶成長前設計特殊結構在藍寶石基板上製作出有規則的圖案，藉以控制發光二極體輸出的發光形式。

螢光粉在製作白光LED元件有著很重要的關係，比如使用綠色螢光粉搭配黃色螢光粉和藍光LED晶粒可以得到高亮度的白光LED元件；使用綠色螢光粉搭配藍光LED晶粒可以直接得到綠光LED元件；使用黃色螢光粉搭配紅色螢光粉及藍光LED晶粒可以得到冷色性質的白光LED元件；也可以使用綠色螢光粉搭配紅色螢光粉與藍光LED晶粒可以得到較高演色性數值的白光LED元件。白光LED元件的演色性指數與藍光LED晶粒、螢光粉及色溫等有直接關係，要達到高演色性除了晶粒覆蓋的波段要長，螢光粉所覆蓋的波段範圍也要長，兩者在可見光光譜上所覆蓋到的波段範圍越大其演色性指數也就越高。

本實驗的部份分為兩個，第一個實驗是利用光學模擬軟體TracePro來模擬擁有圖形化藍寶石基板的發光二極體晶粒，從模擬來得知不同結構的圖形化藍寶石基板對於發光二極體晶粒的發光效率有何影響。

第二個實驗是使用藍光LED晶粒來製作白光元件，藍光LED晶粒波段範圍在450 ~ 452.5 nm，晶粒大小為17*14 mil，以三顆藍光LED晶粒搭配YAG螢光粉(黃綠光 540 nm)製成白光元件，再以另外三顆藍光LED晶粒搭配紅色螢光粉(613 nm)混合綠色螢光粉(519 nm)製成的白光元件進行發光效率比較；搭配YAG螢光粉的白光元件在注入60 mA的電流時所量測到最大的發光效率是在72 lm/W，演色性數值大約為70，CIE色度座標為(0.32, 0.33)，色溫是在5622 °K；而搭配紅色螢光粉混合綠色螢光粉的白光元件在注入60 mA的電流時，最大的發光效率在55 lm/W，演色性數值大約為90，CIE色度座標為(0.31, 0.32)，色溫在6479 °K；證明了藍光LED晶粒搭配紅色螢光粉混合綠色螢光的白光元件演色性指數可以高達90 以上的結果。

關鍵字

發光二極體 ； 圖案藍寶石基板 ； 光學模擬 ； 白光 ； 螢光粉 ； 演色性 ； 紅/綠 ； 釔鋁石榴石

並列摘要

Luminous efficiency of LED（Light-emitting diode）must be improved for general illumination. Two well-known methods to increase luminous efficiency are chip mission-side roughness and substrate surface etching. The patterned sapphire substrate, which is etched regularly before the epitaxy growing in MOCVD, could control the radiation pattern of LED.

Phosphor is one of the most important factors to fabricate white light LED. For examples, high bright white light LED could be made from green or yellow phosphors pumped by blue LED. High efficiency green LED could be fabricated from green phosphor pumping. Cool-white LED could be made from yellow and red emission phosphor. And for lighting or backlighting high CRI（Color Rendering Index）White LED could be fabricated from red and green phosphors pumped by blue LED. Three key issues for color rendering index of white light LED device are blue light LED, phosphor and correlative color temperature. In order to have high color rendering index, two issues described following：wide FWHM（full width at half maximum）and wide phosphor excited light wavelength. If the more covered area of the visible spectrum wavelength we get, the higher CRI we will have.

There are two parts of my experiment. The first is optical simulation by the well-known software TracePro to simulate patterned sapphire substrate. The purpose is to research the effect of different etching structure of patterned sapphire substrate.

The second experiment is to fabricate white light LED from red and green phosphors pumped by blue light LED. The blue light LED we used in our experiment has the wavelength range between 450 and 452.5 nm, and the chip size is 17 mil *14 mil. There are two kinds white light LED we fabricated in the experiment. There are three blue light LED chips bonded in single package of both kinds package. The different of the both packages is mixed phosphor of encapsulation. One of the experimental devices was encapsulated YAG phosphor mixed silicone to fabricate white light. The other is red and green phosphor mixed encapsulation. The compared and focused parameter was luminous efficiency. YAG phosphor pumped white light has the luminous efficiency 72 lm/W, CRI 70, CIE(0.32, 0.33), CCT 5622°K at the operating current 60mA. On another hand, red and green phosphor pumped white light LED has the luminous efficiency 55 lm/W, CRI 90, CIE(0.31, 0.32), CCT 6479°K at the operating current 60mA. We fabricated the red and green phosphor pumped white light LED, and proved that it could has much higher CRI under similar compared conditions, CIE xy and CCT.

並列關鍵字

LED ； Light-emitting diode ； PSS ； Patterned sapphire substrate ； CRI ； Color rendering index ； Phosphor ； Optical Simulaiotn ； Red/Green ； YAG ； White light ； Yttrium-Aluminum-Garnet ； TracePro

參考文獻

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2008年，第113-118頁。