非晶矽薄膜電晶體(a-Si TFTs)應用在液晶顯示器(AMLCD)的周邊電路，已成為眾所注目的焦點。其具有較低的製造成本，可將顯示器周邊電路整合於同一 片玻璃基板上，並被廣泛地研究開發。為了實現所謂的具高附加價值以及有輸入功能的薄型化面板，除了將這些周邊電路整合至玻璃基板，將不同功能之電路整合至畫素上已是必要的考量。尤從各式各樣的不同高階功能如：環境光感測器、影像掃描、觸控式面板等，整合一個非晶矽光感測器似乎是一個最重要的關鍵技術。研究結果顯示α-Si Photo-TFT光電流的大小與光強度呈現良好的線性正相關，且只要是在元件關閉區，不論量測條件為何，線性關係都是成立的。此線性曲線的斜率為光靈敏度，為元件光效應的一個重要參數。在此篇論文中，將討論影響光電流的重要因素如電壓條件、吸收頻譜，以及多晶矽薄膜中的缺陷對其所造成的影響。另外，也研究了額外缺陷態對於光效應的影響；利用在閘極端施加不同電壓的方式，導致能帶中不同種類缺陷的產生，對光效應產生不同的影響。藉此討論劣化區域在多晶矽薄膜中的位置以及它對光電流的效應，並解釋這些不規則的光電流變化與缺陷態的關係。

Amorphous silicon (α-Si) thin-film transistors (TFTs) have attracted much attention in the application of integrated peripheral circuits on display electronics such as active matrix liquid crystal displays (AMLCDs). Various attempts have been reported to integrate display circuits on the glass substrate. In addition, additional pixel circuits are required to realize so-called high-value added display or sheet computer having input function, especially in mobile equipments. Integration ofα-Si optical sensor is considered to have a potential to be a key technology for realizing photo-sensing functions such as ambient light sensors, image scanners, touch panel, etc. It was found that photo current of theα-Si TFT has good linear dependence on the illumination intensity. In the off region, independent of the bias condition, this good linearity is always tenable. In this thesis, we present detailed studies on the characteristics of photo current on bias conditions, photo-response spectrum, and defect states in theα-Si thin film. Furthermore, photo-response of theα-Si TFT affected by extra defect states creation have been also investigated. Different stress condition cause defect states creation , in turn change photo current. The relation between photo leakage current and defect is proposed and explained characteristics the anomalous illumination behaviors after device degradation.

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