非晶氧化銦鎵鋅薄膜電晶體汲極電流在光脈衝下的短時間響應之研究

Abstract

非晶銦鎵鋅氧化物（a-IGZO）薄膜電晶體（TFTs）高度透光的特性，使其可被運用在透明電子產品中，然而在實際應用中在對光和偏壓下所產生的電性不穩定仍是一項待解決的重要問題，因此在這份研究中，我們將探討a-IGZO TFT在變動的光脈衝頻率以及脈寬比之下的汲極電流在正偏壓及光脈衝下的短時間響應行為。由於在光照下產生了不同反應速率的缺陷，其影響了ID曲線的行為，因此為了分析這些缺陷之間的差異，我們對此ID-t圖取微分，於是這些不同反應速率的缺陷能更容易的被分析。進一步地我們由微分結果提出一個公式描述缺陷反應速率，其中擬合參數τ代表了不同反應速率的缺陷，此外我們也了解到此參數和應力時間之間的關係暗示了缺陷的分佈。藉由對公式積分並考慮電荷捕獲效應，我們可以重建並預測原始的響應行為。這份研究不但證明了缺陷的反應機制，且發現到缺陷會隨著應力時間有某一種分佈，可以作為a-IGZO TFTs透明電子產品開發的有用參考。

The highly transparent characteristic of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) makes it possible for the application of the transparent electronics. However, the electrical instability induced by light illumination and gate bias stress is an important issue to be solved in the application. In this study, the short-term response in the drain current (ID) of a-IGZO TFTs under positive bias illumination stress (PBIS) is measured with respect to time in less than 5 seconds under light pulses with altering frequencies and duty ratios. The curves of ID under the light pulses are affected by the different defect reaction rates under light illumination and in the dark. By taking the derivative of the ID-t curves, the defects with different reaction rates can be extracted, and the different behaviors between the excited and recovering parts become clear. Further, a fitting formula is proposed to analyze the defect behaviors, while the fitting parameters τ represent defect of different reaction rates. Besides, the correlation between the parameters τ and the stress time implies the spread of defects. The original behavior of ID in response to light pulses can be fairly reconstructed by the integrating the differential values from the fitting formula with a correction factor of charge trapping. This study substantially proves the mechanism in the time response to light illumination and provides a new method to analyze the defect behaviors, which can be a helpful reference in the development of transparent products using a-IGZO TFTs.