Browsing by Author "Kuo, Yan-Fu"

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An Empirical Defect-Related Photo Leakage Current Model for LTPS TFTs Based on the Unit Lux Current
(2010-05-01)
Tai, Ya-Hsiang
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Kuo, Yan-Fu
;
Sun, Guo-Pei
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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 (LTPS) thin-film transistors (TFTs) after dc stress is analyzed. It is found that the illumination behaviors for poly-Si TFTs are dependent on the defect types created by different stress conditions of hot-carrier and self-heating effects. For a given stress-induced device degradation, the anomalous illumination behaviors are observed, and these photo-induced leakage currents are not included in the present SPICE device model. Therefore, based on trap-assisted and Poole-Frenkel effect, an empirical defect-related photo leakage current model based on Unit Lux Current (ULC) is proposed to depict the photo-induced current after device degradation. Furthermore, the verified equation of ULC is analytically derived and has good agreement with the experimental data.
Capacitance-voltage behaviors of the LTPS TFTs before and after DC stress explained by the slicing model
(2007)
Kuo, Yan-Fu
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Huang, Shih-Che
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Chao, Yu-Te
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Tai, Ya-Hsiang
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光電工程學系
The proposed analytical circuit based on the slicing model further explains the behavior of the gate-to-source capacitance CGS and gate-to-drain capacitance CGD curves of the LTPS TFT at different measuring frequencies. The degradation mechanisms and damaged locations can be identified according to the frequency responses of the CGS and CGD curves.
Dependence of Photosensitive Effect on the Defects Created by DC Stress for LTPS TFTs
(2008-12-01)
Tai, Ya-Hsiang
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Kuo, Yan-Fu
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Lee, Yun-Hsiang
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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.
Dynamic stress effects on the reliability of poly-Si TFT
(2007)
Kuo, Yan-Fu
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Huang, Shih-Che
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Shih, Wei-Lun
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Tai, Ya-Hsiang
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光電工程學系
The degradation of poly-Si TFT under different gate pulse waveforms is investigated. The mobility degradation is analyzed with the lateral transient electric field and carrier numbers near the channel edges. A proposed index fairly depicts the device degradation, which is helpful in evaluating lifetime for the poly-Si TFT circuits.
Gap-Type a-Si TFTs for Backlight Sensing Application
(2011-08-01)
Tai, Ya-Hsiang
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Chou, Lu-Sheng
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Kuo, Yan-Fu
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Yen, Shao-Wen
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光電工程學系
In this paper, a new photo device are proposed using gap-typed hydrogenated amorphous silicon (a-Si: H) thin-film transistors (TFTs) as backlight sensing circuits. The system employs gap type a-Si TFTs, which has higher photo sensitivity, to sense illumination and increase device dynamic range. Meanwhile, the system with local dimming technologies could attain the purpose for self-adjusting function. It is expected that the integration of this sensing system onto the panel can be implemented without extra process development. Furthermore, the photo leakage characteristics of a-Si TFTs after optical stress are investigated and the corresponding calibration method is proposed to reduce the error in sensing the illumination intensity. This approach would provide the possibility for the sensors array to be integrated into the pixel with the same a-Si TFT device.
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.
Self-Modulated Amorphous Front and Back Light Sensors with Wide Dynamic Range
(2009)
Kuo, Yan-Fu
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Yu, Teng-Jui
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Yen, Shao-Wen
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Tai, Ya-Hsiang
;
光電工程學系
Source gate and partial floating dual gate structure of a-Si TFTs and its illumination effect are used to make front and back light sensors. The proposed system employs novel device to sense illumination for wide dynamic range. It's expected the integration of sensing system onto the panel without extra process.
Statistical study on the temperature dependence of the turn-on characteristics for p-type LTPS TFTs
(2007-08-01)
Kuo, Yan-Fu
;
Tai, Ya-Hsiang
;
光電工程學系
;
顯示科技研究所
;
Department of Photonics
In recent years, low temperature polycrystalline silicon (LTPS) thin-film transistor (TFT) has been widely investigated for various applications to system-on-panel (SOP) technology. However, due to the complexity of grain boundary trap properties, the conducting behaviors of various LTPS TFTs are difficult to be analyzed systematically. In this paper, the common and device-dependent thermal effects are studied to understand the conduction mechanism in the UPS TFTs. (c) 2007 Elsevier Ltd. All rights reserved.