脈衝雷射對發光二極體光萃取效率之影響

Light Extraction Enhancement of Light Emitting Diodes by the Pulse Laser

陳肇祈(Zhou-Chi Chen)

指導教授 ： 李有璋

中原大學/工學院/機械工程研究所/碩士(2011年)

https://doi.org/10.6840/cycu201100884

摘要

本研究最主要的目的是利用脈衝雷射蝕刻製作週期性微/奈米結構在發光二極體(Light emitting diodes, LEDs)之透明導電膜(Transparent Conducting Oxide, TCO)表面，藉此,破壞內部全反射以提升發光二極體之光萃取效率。在雷射製作週期性奈米結構上，奈秒長脈衝雷射是透過表面散射波與雷射光干涉後產生波紋(Ripple)奈米結構；飛秒超短脈衝雷射則是利用表面散射波與表面電漿相互干涉後形成二次諧振波，進而產生波紋奈米結構。且雷射光束透過高斯平坦化後照射於透明導電膜上能夠大幅增加奈米波紋奈米結構的出現。在提升光萃取效率上，由於飛秒雷射的能量分佈屬於高斯曲線，製程後傷及發光二極體內部p-型氮化鎵，因此提升出光效率並不明顯，僅有上升16.36%，其順向偏壓已超過±0.1 V的誤差範圍。相對於透過高斯平坦化(Beam Shaping)後的奈秒雷射，出光效率大幅提升至24%，顯示雷射製程並未對發光二極體本身電特性有任何的影響，而在製程後發光二極體的順向偏壓仍與傳統3.029伏特幾乎相同。

關鍵字

雷射誘發週期性表面結構 ； 發光二極體 ； 飛秒超短脈衝雷射

並列摘要

In this study, pulsed lasers were used to fabricate micro/nano structures on the transparent conducting oxide (TCO) layers of the light emitting diodes (LEDs) to destroy the total internal reflectionat TCO/air and enhance the light extraction efficiency. The formation of laserinduced periodic surface structures (LIPSS) depends on the pulsed duration. For nanosecond laser, LIPSS was attributed to the interference of surface scattering wave and incident laser, but second harmonic wave generated from the interference of surface scattering and surface plasma induces ripples for the femtosecond laser. This study showed that light-emitting efficiency increases with surface roughness by femtosecond laser, and achieved an improvement of 16.46 %. But the forward voltage is also higher through femtosecond laser processing, meaning the laser fluence damaged the p-GaN. However, light output power enhanced to 24% and the forward voltage was not changed after nanosecond laser processing, this showed that flat-top beam of nanosecond laser was only fabricate ripple structure but not damaged the electrical property of LED.

並列關鍵字

Ultra short pulsed laser ； LIPSS ； Light emitting diodes

參考文獻

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