Browsing by Author "Kao, Shih-Chin"

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Amorphous indium-gallium-zinc-oxide visible-light phototransistor with a polymeric light absorption layer
(2010-11-15)
Zan, Hsiao-Wen
;
Chen, Wei-Tsung
;
Hsueh, Hsiu-Wen
;
Kao, Shih-Chin
;
Ku, Ming-Che
This work demonstrates a real-time visible-light phototransistor comprised of a wide-band-gap amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) and a narrow-band-gap polymeric capping layer. The capping layer and the IGZO layer form a p-n junction diode. The p-n junction absorbs visible light and consequently injects electrons into the IGZO layer, which in turn affects the body voltage as well as the threshold voltage of a-IGZO TFT. The hysteresis behavior due to the charges at IGZO back interface is also discussed. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3517506]
Amorphous indium-gallium-zinc-oxide visible-light phototransistor with a polymeric light absorption layer
(2010-11-15)
Zan, Hsiao-Wen
;
Chen, Wei-Tsung
;
Hsueh, Hsiu-Wen
;
Kao, Shih-Chin
;
Ku, Ming-Che
This work demonstrates a real-time visible-light phototransistor comprised of a wide-band-gap amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) and a narrow-band-gap polymeric capping layer. The capping layer and the IGZO layer form a p-n junction diode. The p-n junction absorbs visible light and consequently injects electrons into the IGZO layer, which in turn affects the body voltage as well as the threshold voltage of a-IGZO TFT. The hysteresis behavior due to the charges at IGZO back interface is also discussed. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3517506]
Modeling of the parasitic resistance effect in poly-Si TFTs with LDD structure
(2005)
Kao, Shih-Chin
;
Zan, Hsiao Wen
;
Chen, Shih-Ching
;
光電工程學系
;
Department of Photonics
In this study, the model of poly-Si TFTs with LDD structure had been proposed. Firstly, parasitic resistance parameters were extracted from devices with various channel length and LDD length. Then, an accurate I-V model was constructed by combining basic TFT model (RPI model) and the parasitic resistance effects. The model had been verified for devices with channel length larger than 6 mu m. The transconductance behavior in both linear region and saturation region are also well explained by our proposed model.
New Organic Phototransistor With Bias-Modulated Photosensitivity and Bias-Enhanced Memory Effect
(2009-07-01)
Zan, Hsiao-Wen
;
Kao, Shih-Chin
;
光電工程學系
;
Department of Photonics
A simple and effective method to adjust organic thin-film transistor photosensitivity was proposed. First, the full suppression of light-induced threshold-voltage shift was successfully demonstrated by applying negative gate bias during illumination. Then, the light-induced threshold-voltage shift that was modulated from 0 to 13.5 V was achieved by changing the drain and source bias from +15 to -15 V. Plausible mechanisms were proposed and verified. After light removal, the memory ability of the threshold-voltage shift was also greatly enhanced by the bias effect. The results demonstrate a sensitive organic phototransistor with memory ability by adjusting suitable bias conditions.
Organic Photo Transistors with Drain Bias Modulation Effect
(2008)
Zan, Hsiao-Wen
;
Kao, Shih-Chin
;
光電工程學系
;
Department of Photonics
In this paper, the influence of light induced electrons on the threshold voltage shift of organic thin film transistors (OTFTs) was studied. The light induced electrons are formed and accumulated in the channel near the interface of gate dielectric. The light source can be used as second source. Therefore, the study demonstrates the light induced electrons in channel can be affected by drain bias like bias stress. The decreasing accumulated electrons with increasing positive drain bias lower the threshold voltage shift rate during illumination time. The opposite trend can be observed when using negative drain increases accumulated electrons. This result is helpful to adjust the photosensivity of organic photo transistors.
Oxygen-Dependent Instability and Annealing/Passivation Effects in Amorphous In-Ga-ZnO Thin-Film Transistors
(2011-11-01)
Chen, Wei-Tsung
;
Lo, Shih-Yi
;
Kao, Shih-Chin
;
Zan, Hsiao-Wen
;
Tsai, Chuang-Chuang
This letter discusses the reason for the instability of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) under both positive and negative bias stresses. This instability is significantly influenced by the oxygen content in the bulk IGZO and the surrounding environment. The as-fabricated low-temperature devices can only endure a single polarized bias stress. An a-IGZO TFT that is stable toward both positive and negative bias stresses with large relaxation times of 95 x 10(4) and 371 x 10(4) s, respectively, is achieved by annealing and passivation.
Pentacene-Based Organic Phototransistor With High Sensitivity to Weak Light and Wide Dynamic Range
(2010-02-01)
Zan, Hsiao-Wen
;
Kao, Shih-Chin
;
Ouyang, Shiang-Ruei
;
光電工程學系
;
Department of Photonics
In this letter, the channel length effect, combined with the photoelectric field effect of organic phototransistors, has been investigated for the first time. Reducing the channel length and applying a positive gate bias during illumination enhance electron trapping effectively and hence improve the photoresponsivity of a pentacene-based phototransistor. The sensing dynamic range and the photosensitivity to very weak light (in the range of microwatts per square centimeter) are also discussed through the interaction between deep trapped states, interface energy-band bending, and photoexcited electrons.
Self-Heating Effect on Bias-Stressed Reliability for Low-Temperature a-Si:H TFT on Flexible Substrate
(2010-03-01)
Kao, Shih-Chin
;
Zan, Hsiao-Wen
;
Huang, Jung-Jie
;
Kung, Bo-Cheng
;
光電工程學系
Hydrogenated amorphous silicon thin-film transistors on colorless polyimide substrates were successfully fabricated at a low process temperature (160 degrees C). The gate leakage current is as low as 10(-13) A, while the field-effect mobility is 0.42 cm(2)V(-1) . s(-1), and the subthreshold swing is 0.77 V/dec. Using bias-temperature stress on devices with different channel widths, the enhancement of self-heating effect on bias-stressed reliability is investigated for the first time. Elevated temperature due to self-heating effect is estimated either by extending the bias-stressed model or by modifying the thermal equivalent circuit model. Degradation of device reliability on a bent substrate is also significant when self-heating effect is incorporated.
Study on Oxygen-dependent Instability of Amorphous In-Ga-Zn-O TFT and Completely Stable Device under Both Positive and Negative Bias Stresses
(2010)
Chen, Wei-Tsung
;
Zan, Hsiao-Wen
;
Lo, Shih-Yi
;
Kao, Shih-Chin
;
Tsai, Chuang-Chuang
A complete experiment is conducted to verify the origin of stress-induced instability in an amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT). It is found that the oxygen ratio in an IGZO layer strongly influences the device stability under bias stress. For realizing an adequately stable device, post-annealing and passivation are performed in order.
The modified bias-stress effect in organic TFTs
(2007)
Zan, Hsiao-Wen
;
Kao, Shih-Chin
;
Pan, Huang-Wei
;
Lin, Kun Chih
;
Hsu, Chen Chou
In this paper, the influence of drain bias on the bias stress effect in pentacene-based organic thin-film transistors was studied. It was found that, under gate bias stress measurement, the threshold voltage shift was strongly affected by the drain bias due to the varied channel charge amount. As a result, conventional stretched-exponential function was modified with a channel charge normalization factor to describe the dependence of threshold voltage shift on the stressing time. The result is important for the design of organic electronic or OTFT active-matrix display, in which the influence of both the gate and the drain biases has to be considered.