脈衝光照及正向偏壓下對非晶氧化銦鎵鋅薄膜電晶體時間響應之研究

Abstract

利用非晶氧化銦鎵鋅(a-IGZO)薄膜電晶體(TFTs)具高透光性的特點，可發展透明電子產品，但對光和偏壓下產生的不穩定性會影響實際應用的操作，因此在這份研究中，將探討脈衝光照及正向偏壓下的時間響應。我們藉由量測單一脈衝光及正向偏壓下汲極電流隨時間的變化來研究照光之時間響應，首先觀察到正向偏壓下的不穩定性也會對時間響應有所影響，且可以被視做為背景並予以扣除。我們更進一步地提出照光時間響應之公式來描述照光行為，並解釋其反應機制為氧空缺與光誘發的電子電洞對的結合。在真實環境中使用透明電路，元件照光情況不會只有一次，故我們以多個脈衝光照射元件，在相同偏壓下進行量測，結果發明，仍可以用相同的擬合公式及參數進行擬合，這些多個脈衝光照的結果與單一脈衝光照之證明了擬合公式及反應機制的可用性。本研究所提出的時間響應模型及機制，可做為透明a-IGZO TFTs產品開發的重要參考。

The unique feature of high transparencyfor a-IGZO TFTs makes the development of the transparent electronics possible. However, the instability induced by light illumination as well as the gate bias may hinder the practical applications. In this work, the time response of the TFTs under light illumination and bias stress is studied. By measuring the drain current change with time under single light illumination and positive gate bias (PBS), the time response is investigated. We observed that the positive bias stress instability would play a part of the time response for light illumination. The PBS instability is taken as the background and can be deducted separately. Further, we propose the fitting formula of time response for light illumination to describe the behavior which can be explained by the proposed mechanism. The mechanism is correlated to the oxygen vacancy reacting with the light-induced electron-hole pairs. In real situations, the devices in the transparent electronics are rarely illuminated only for once. We therefore further studied the time response to the multiple-pulse illumination and found that it can be fitted by the same formula and parameters. This study substantially proves the model and mechanism of time response to the light illumination. It reveals the possibility to use the proposed fitting formula in the more complicated illumination cases, which can be an important reference for the development of transparent products using a-IGZO TFT.