銦錫氧化物薄膜表面處理改善 氮化鎵發光二極體之發光效率

Improvement in light efficiency of GaN/InGaN light-emitting diodes by surface treatment of indium-tin-oxide thin film

魏健榮(Chien-Jung Wei)

指導教授 ： 劉宗平

元智大學/電機通訊學院/電機工程學系/碩士(2007年)

https://doi.org/10.6838/YZU.2007.00099

摘要

銦錫氧化物(indium-tin-oxide，ITO)，薄膜具有極佳的導電性質，在可見光區具有高的透射率，在紅外光區具有高的反射性。因此，透明導電膜一直是學術界及工業界積極研究及分析的對象，它可以廣泛地被應用包括透明加熱元件、液晶顯示器、發光二極體以及電子，光學及光電裝置中的抗反射鏡和熱反射鏡。
在此研究中，針對氮化鎵發光二極體的銦錫氧化物薄膜進行表面處理，以期改善二極體之發光效率。首先利用電子槍蒸鍍技術將四分之一波長整數倍的ITO薄膜沉積在玻璃基板上，當此薄膜具有高的透射率和低的片電阻時，便可做為氮化鎵發光二極體中p-GaN層上的透明導電層。接著，使用化學溶劑來粗化ITO薄膜的表面粗度，以期改善氮化鎵發光二極體出射光的效率。
在量測方面，利用表面粗度儀(α-step)來測量ITO膜之厚度，以四點探針(our point probe)系統來量測片電阻。再利用光譜儀來分析位在400 nm到600 nm波長範圍內的透射率光譜，並以HP4155B來量測氮化鎵發光二極體樣品的I-V特性曲線，為了觀察ITO薄膜表面的微結構，利用AFM(atomic force microscope) 來觀察薄膜表面的形貌，並分析粗化的效果。實驗量度數據顯示，ITO薄膜粗化後，氮化鎵系列發光二極體出射光的效率大幅提升了。

關鍵字

氮化鎵發光 二極體 ； 銦錫氧化物薄膜 ； 表面處理 ； 濕蝕刻

並列摘要

The film composed of indium-tin-oxide (ITO) had been widely studied by the academia and the industrial circle due to it’s excellent conducting property, high transmittance in the visible region, and high reflectance in infrared region. The transparent conducting ITO film can be applied in transparent heating elements, LCDs (liquid crystal display),LEDs (light-emitted diode), and anti-reflection and heat reflecting mirrors on the electronic,optical or photoelectric devices.
In this study, the surface treatment of ITO films were made to improve the light efficiency of GaN LED. Firstly, the thickness of 1/4 integer of wavelength of the ITO films were deposited on glass substrate by the e-gun evaporation technique. As the ITO film with high transmittance and low sheet resistance was obtained for it can be need as the transparent conducting layer on p-GaN of GaN LED. Then, the surface roughness of the ITO film can be changed by chemical solution to etch the surface to improve the emergent-light efficiency of GaN LED.
The thickness and sheet resistance of ITO film were measured by alpha step and four point probe system, respectively. The transmittance spectra of the ITO film in the range of 400 nm to 600 nm studied through
spectroscopy. The I-V characteristic curve of GaN LED sample was obtained with HP4155B. Consequently, the AFM was needed to observe the morphology of ITO films to analysis the microstructure of the surface roughness. Experimental data show that the emergent-light efficiency of GaN/InGaN LED can be largely raised by the surface treatment of ITO films.

並列關鍵字

GaN LED ； ITO film ； surface treatments ； wet etching

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