Browsing by Author "Lee, Yun-Hsiang"

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Dependence of Photosensitive Effect on the Defects Created by DC Stress for LTPS TFTs
(2008-12-01)
Tai, Ya-Hsiang
;
Kuo, Yan-Fu
;
Lee, Yun-Hsiang
;
光電工程學系
;
顯示科技研究所
In this letter, the photosensitive effect of n-type low-temperature polycrystalline silicon (LTPS) thin-film transistors (TFTs) after dc stress was investigated. It was discovered that the photo-generated carrier behaviors under optical illumination are related to defect types created by different stress conditions of hot-carrier effect and self-heating effect. These two types of defect creation result in the different photosensitivity behaviors of LTPS TFT. A model considering the relation between photosensitivity and defect is proposed to explain the anomalous illumination behaviors after device degradation.
Photosensitivity Analysis of Low-Temperature Poly-Si Thin-Film Transistor Based on the Unit-Lux-Current
(2009-01-01)
Tai, Ya-Hsiang
;
Kuo, Yan-Fu
;
Lee, Yun-Hsiang
;
光電工程學系
;
顯示科技研究所
In this paper, the photosensitive effect of n-type low-temperature polycrystalline-silicon thin-film transistors (TFTs) is investigated. A novel layout is adopted to demonstrate that the photo leakage current occurs in the depletion region at the drain junction. Based on the Poole-Frenkel effect lowering of a coulombic barrier and phonon-assisted tunneling, it is discovered that the photosensitivity behavior for poly-Si TFT is dependent on the gate and drain bias. However, this photoinduced leakage current behavior is not included in the present SPICE device model. Therefore, a new parameter, unit-lux-current (ULC), is proposed to depict the photoinduced current. Its dependence on the gate/drain bias and temperature is discussed, and the equation of ULC is further derived, which has good agreement with the experimental data. A qualitative deduction is developed to account for the photo leakage mechanism. ULC variation with respect to defect states in the drain region is also discussed.