偏壓以及照光下 非晶氧化銦鎵鋅薄膜電晶體之雜訊行為研究

Abstract

在本文中，我們探討光效應會對其非晶氧化銦鎵鋅薄膜電晶體雜訊的影響。首先，我們將量測元件的雜訊頻譜進行積分計算以得到雜訊電流，此做法可以減少頻譜所造成的誤差。和無照光的元件相比，發現照光後元件產生的雜訊明顯較多，因此想藉由光強的變化來探討雜訊行為；我們發現，即使汲極電流對應的閘極電壓會有所不同，當發光越強時，在相同汲極電流下所產生的雜訊值越多；即使量測的順序會影響汲極電流-閘極電壓的特性，但其與汲極電流的關係，在固定光強之下，相同汲極電流下產生的雜訊值，不因照光的歷程而有變化。 經過分析，此雜訊被認為Hooge模型提出的遷移率擾動所導致。載子散射效應和遷移率擾動有相當密切的關係。使用此模型做雜訊相關的計算，我們發現Hooge參數會隨著光強的增強而增加。我們推測在照光的情形下，氧空缺的變化會造成散射效應的改變，進而造成雜訊值的上升。經由此研究，可了解雜訊產生的情形，期望有助於在未來應用在畫素感測器中，可達到更好的成像品質。

In this thesis, we investigate the response of noise for the a-IGZO TFTs to the light intensity. The measured spectrum of device is calculated by integration to reduce the error caused by the spectrum fluctuation. Compared with the case of non-illumination, the noise level increases, which make us interested in the study of noise behavior with respect to the light intensity. In the experiment of changing light intensity, we find that the induced noise with respect to the same drain current (ID) gets more with illumination even though the ID corresponded gate voltage (VG) can be different. With fixed intensity, the noise induced at the same ID is not changed regardless of the illumination history.

After the analysis, the noise is thought to be caused by the mobility fluctuation which model is proposed by F. N. Hooge. There is a close relationship between the scattering effect and mobility fluctuation. By the calculation based on this model, we discover that when the light intensity rises, the Hooge’s parameter is larger. We speculate that oxygen vacancy affects the scattering and leads to the noise increasing with illumination. Through this study, we can better understand the noise generation situation with illumination. It is expected to be helpful for the future applications in design of pixel light sensing circuit to achieve better imaging quality.