低溫複晶矽薄膜電晶體背光下之單位光通量漏電流特性分析

Abstract

低溫多晶矽薄膜電晶體(LTPS TFTs)已被廣泛研究在平板的應用，例如在主動式矩陣液晶顯示器(AMLCDs)和主動式矩陣有機發光二極體(AMOLEDs)。高亮度的背光照明下，光漏電流的存在容易造成畫素電壓的下降而導致串音(Cross talk)的產生。因此，光對低溫薄膜電晶體是值得調查。 在這篇論文中，我們分析了低溫複晶矽薄膜電晶體在背光照明下影響的光漏電流。我們漏電流在背光下可用一個經驗公式表示。我們也比較了背光和正光條件下的光行為。定性模型來解釋在熱載子效應(Hot Carrier effect)與自發熱(Self Heating effect)後產生的缺陷提出相應的光照行為。缺陷中心影響光漏電流的行為與缺陷陷阱的能級非常相關。在直流偏壓後有兩種缺陷造成。我們提供新的見解之間的連接缺陷能級和光感應電流，從而進一步確認缺陷的特性。我們相信，這項研究的背光感應漏電流在設計中考慮是非常有用，並減少漏電流在薄膜電晶體液晶顯示器中。

Low temperature polycrystalline silicon (LTPS) thin film transistors (TFTs) have been widely investigated for flat-panel applications, such as for active matrix liquid crystal displays (AMLCDs) and active matrix organic light emitting diodes (AMOLEDs). The high illumination intensity from back light increases the leakage current of LTPS TFTs and results in the decrease of pixel voltage and the increase of cross talk. Therefore, photo effect on LTPS TFTs is worthy of investigation. In this thesis, we analyze the effect of back light illumination for LTPS TFTs based on the photo leakage current. The leakage current under back light can be expressed by an empirical equation. We also compare the photo behaviors of back light with that of front light condition. Qualitative models are proposed to explain the illumination behaviors corresponding to the defects created after hot carrier stress and self heating stress. Defect center behaviors which influence the photo leakage current are strongly related to the energy level of trap defects. There are two kinds of defects created by DC stress. We provide new insight on the connection between the energy levels of the defects and the photo induced current, which can further confirm the characteristics of the defects. We believe this study of the backlight induced leakage current can be very useful in the design consideration and the leakage current reduction in the TFT LCD.