氧化銦錫透明電極應用於氮化鎵發光二極體

Abstract

本論文利用射頻磁控濺鍍法濺鍍氧化銦錫透明導電薄膜分別於石英玻璃與p型氮化鎵之上，首先濺鍍於石英玻璃上探討製程參數對ITO導電薄膜的光學特性以及電學性質的影響；其後將ITO濺鍍在p型氮化鎵上研究透明導電薄膜與半導體間的接觸特性，最後用於發光二極體元件上對於元件特性作一分析。 從實驗中發現在室溫下所濺鍍出的氧化銦錫導電薄膜，利用快速熱退火處理在氮氣環境下可以有效的降低片電阻值，並且在600oC退火時間30秒時得到最低的片電阻值為12.18Ω/□且在藍光區透光度為80％以上。並且從XRD的分析上得到在氮氣環境下退火氧化銦錫薄膜從非晶結構到以（222）方向為擇優取向，而氧氣環境下退火則發現薄膜呈現（400）方向為擇優取向。再與薄膜的電學特性作比較發現以此方法濺鍍出的ITO薄膜（222）的結晶方向較有利於載子的傳導因此有較佳的電阻值。並且在霍爾量測的結果得到氮氣環境下退火的薄膜可以有效的活化內部的載子以此做一印證。並且從穿透光譜所量測出來的結果發現退火中所使用的氣體，使用氮氣的比例含量提高則穿透光譜的峰值有往短波長移動的趨勢。 而使用NiO作為ITO與P型氮化鎵接觸的介層，在氧氣環境下退火550oC30秒所得到的特性接觸電阻將有效的改善至2.26 x10-3 Ω-cm2，而在製程上應用至氮化鎵發光二極體得到啟動電壓為3.28V與阻值為47.8Ω，並且發光二極體的發光強度提升的50％。

ABSTRACT In this thesis, the ITO films deposition were carried out by R.F. magnetron sputtering system and the films were deposited on both glass and p-GaN substrate at room temperature. Two main issues were investigated. First, we deposited the ITO films on glass substrate to study the process parameter effects on the optical and electrical properties. Then the contact properties between ITO and p-GaN were studied . The behavior of LEDs with ITO and Ni/Au was discussed. The lowest sheet resistance of the ITO films deposited at room temperature was obtained by post rapid thermal annealing at 600OC for 30sec in N2 ambient. XRD measurement showed that the (222) preferred orientation was obtained after annealed in nitrogen ambient, and (400) preferred orientation in oxygen ambient. The transmittance spectra peak shift to short wavelength with increased the nitrogen composition in annealing ambient. Using NiO as an interlayer between the ITO and p-GaN can reduced specific contact resistance to 2.26 x10-3 Ω-cm2. Light output power of LED with ITO transparent contact was enhanced about 50% compared with LEDs with Ni/Au transparent contact.