以底切方法改變晶粒幾何結構來提升發光二極體量子效率之研究

The study of quantum efficiency improvement for LED chips by using geometrically undercut deformation

楊政育(Cheng-Yu Yang)

指導教授 ： 周永燦

中原大學/電機資訊學院/工業與系統工程研究所/碩士(2012年)

https://doi.org/10.6840/cycu201200694

摘要

隨著發光二極體的快速發展，其應用範圍也隨之擴展，已漸漸取代日常生活中的照明，成為日常生活中不可或缺的重要元件，然而發光二極體發展至今，提升元件的內部量子效率已不足以大幅提升元件的總光量，外部量子效率又因為內部的吸收及全反射所造成的光損失，使得光子只能在內部全反射直到被吸收殆盡，造成發光效率不佳，而利用蝕刻技術使元件的結構改變是本研究主要提升量子效率的方法。
由於一般傳統的濕式蝕刻無法對氮化鎵進行有效蝕刻，因此本研究以高溫濕式蝕刻方式，利用硫酸與磷酸兩種酸性混合液體調製所需之蝕刻溶液，在320℃的高溫下進行化學濕式蝕刻，並使用抗蝕刻的二氧化矽做為蝕刻阻擋層，藉由化學濕式蝕刻具有等向性蝕刻的特性，製備出具有底切形狀之發光二極體，利用晶粒底切形狀的改變來提升現有發光二極體的量子效率。
待晶粒底切幾何結構發光二極體製備完成後，以掃描式電子顯微鏡檢測其外觀，再利用光束角做光型態分析，最後再以積分球量測底切幾何結構對電性及光性之影響。由實驗結果我們得知，晶粒底切幾何結構發光二極體確實狀破壞了出射光的反射路徑，使發光效率有所提升，元件的外部量子效率增加了4.98%，光束角增加了3.75度，而最大正向光強度也提高了12.4%。此外，本研究之晶粒底切結構發光二極體應用在手機背光源、液晶螢幕背光源及電視螢幕背光源的量產測試上，亦能高出傳統發光二極體約5%的發光效率。

關鍵字

底切 ； 高溫濕式蝕刻 ； 發光二極體 ； 二氧化矽

並列摘要

With the rapid development in the technology of light-emitting diodes (LEDs), the scope of LEDs applications also will be expanded. They have gradually replaced lighting in our daily life and become an indispensable component. Improving the LEDs’ internal quantum efficiency is not enough to significantly improve the device's total light output power because of the external quantum efficiency caused by the absorption and total reflection of the internal optical loss. This causes the photons only in the total internal reflection until it had been absorbed, resulting in poor luminous efficiency. To enhance the quantum efficiency, geometric deformation by etching is the major method in this study.
Conventional wet etching can not be effective etching of GaN. In this study, we use the high-temperature wet etching , the two acid mixture of H2SO4 and H3PO4 etching solution under the chemical wet etching in a high temperature of 320℃, while using the SiO2 as an etching hard mask, Utilizing the isotropic characteristic of chemical wet etching, LEDs with undercut structure are fabricated in this experiment, improving the quantum efficiency by undercut geometry structure.
When the undercut geometry structure of light-emitting diode system is prepared to completion, we use the SEM to see the undercut’s morphology, and then light pattern is analyzed from its beam angle, to obtain the electrical and optical properties’ measurements. From the experimental results, we know that the undercut geometry structure of light-emitting diodes does status destruction order to the reflection of the beam path, so that the light output power efficiency has improved . The external quantum efficiency increased by 4.98% with undercut structure LEDs, beam angle to increase by 3.75 degrees, and the maximum positive light intensity also increased by 12.4%. Finally, in mobile phone, LCD, and TV monitor back light applications, luminous efficiency of proposed LEDs can be 5% higher than general ones.

並列關鍵字

SiO2 ； undercut ； LED ； high-temperature wet etching

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