Browsing by Author "Tsai, Wu-Wei"

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A 1-V operated polymer vertical transistor with high on/off current ratio
(2009)
Chao, Yu-Chiang
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Tsai, Wu-Wei
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Chen, Chun-Yu
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Zan, Hsiao-Wen
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Meng, Hsin-Fei
Dependence of Light-Accelerated Instability on Bias and Environment in Amorphous Indium-Gallium-Zinc-Oxide Thin Film Transistors
(2013)
Chen, Yu-Chun
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Chang, Ting-Chang
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Li, Hung-Wei
;
Chung, Wan-Fang
;
Hsieh, Tien-Yu
This study examines the dependence of light-accelerated instability on bias and environment in amorphous indium-gallium-zinc-oxide thin film transistors. When device is in vacuum ambient, the threshold voltage of device after negative gate bias illumination stress (NBIS) showed bias-dependent electrical degradation behavior. However, experimental results show the degradation of electrical characteristic in a-IGZO devices does not only rely on the charge trapping mechanism for NBIS. During NBIS in oxygen, moisture-simulated and atmosphere ambient, the negative shift in electrical characteristic is suppressed when compared to that in vacuum. This implies that the adsorbent gas species in the surrounding environment dominates the electrical characteristic degradation of devices during NBIS, which leading the change of dominant mechanism from photon-created carrier trapping to adsorbed/desorbed gas phenomenon. (C) 2013 The Electrochemical Society. All rights reserved.
Effective Mobility Enhancement by Using Nanometer Dot Doping in Amorphous IGZO Thin-Film Transistors
(2011-10-04)
Zan, Hsiao-Wen
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Tsai, Wu-Wei
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Chen, Chia-Hsin
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Tsai, Chuang-Chuang
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光電工程學系
High output current in vertical polymer space-charge-limited transistor induced by self-assembled monolayer
(2012-08-27)
Zan, Hsiao-Wen
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Hsu, Yuan-Hsuan
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Meng, Hsin-Fei
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Huang, Chian-Hao
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Tao, Yu-Tai
We present a promising solution-processed vertical transistor which exhibits high output current, high on/off current ratio, and low operation voltage. Numerous poly(3-hexylthiophene) vertical channels are embedded in vertical nanometer pores. Treating the sidewalls of pores by self-assemble monolayer with long alkyl chains enhances the pore-filling and inter-chain order of poly (3-hexylthiophene). The channel current is therefore greatly increased. A grid metal inside the porous template controls the channel potential profile to turn on and turn off the vertical transistor. Finally, the transistor delivers an output current density as 50-110 mA/cm(2) at 2V with an on/off current ratio larger than 10 000. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4748284]
Increasing organic vertical carrier mobility for the application of high speed bilayered organic photodetector
(2009-11-23)
Tsai, Wu-Wei
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Chao, Yu-Chiang
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Chen, En-Chen
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Zan, Hsiao-Wen
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Meng, Hsin-Fei
The direct influence of the vertical carrier mobility on the frequency response of bilayered organic photodiodes (PDs) is investigated for the first time. With fullerene as the acceptor material, changing vertical hole mobility from 2.3x10(-5) to 2.8x10(-4) cm(2)/V s increases PD bandwidth from 10 to 80 MHz under a 4 V operation. The influence of deposition rate on vertical hole mobility of pentacene film is also discussed. Our results facilitate the application of bilayered organic PDs on the detection of very-high-frequency optical signals.
Investigation of gate-bias stress and hot-carrier stress-induced instability of InGaZnO thin-film transistors under different environments
(2013-09-01)
Hsieh, Tien-Yu
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Chang, Ting-Chang
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Chen, Te-Chih
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Tsai, Ming-Yen
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Chen, Yu-Te
This paper investigates the temperature and ambiance effects on various reliability issues for InGaZnO thin film transistors with an organic passivation layer. Hot-carrier stress and gate-bias stress are carried out under different environmental temperatures and ambient gases. The device exhibits relatively good stability under room temperture, whereas high temperature enhances degradation. Futhermore, different degradation behaviors after gate-bias stress in atmosphere and in vacuum can be attributed to gas adsorption/desorption-induced instability. Moreover, capacitance-voltage measurement techinique is utilized to analyze the degradation mechanism and to extract the density of state (DOS). The result reveals that the threshold voltage shift after both hot-carrier and gate-bias stress originates from the charge-trapping effect at the interface of gate insulator and active layer, with the extra trap states generated during stress responsible for C-V curve distortion. In addition, the asymmetric degradation behavior of gate-to-drain capacitance (Cgd) and gate-to-source capacitance (Cgs) indicates that trap states are generated near the drain side. (C) 2012 Elsevier B.V. All rights reserved.
Pentacene-Based Organic Thin Film Transistors for Ammonia Sensing
(2012-03-01)
Zan, Hsiao-Wen
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Tsai, Wu-Wei
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Lo, Yen-ren
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Wu, Yu-Mei
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Yang, Yuh-Shyong
Non-invasive ammonia sensors are attractive alternatives for the diagnoses of a variety of chronic diseases such as liver cirrhosis and renal failure. A low cost pentacene-based organic thin film transistor (OTFT) fabricated by a novel and simple process was demonstrated to be highly sensitive and specific for ammonia gas. Various measurement parameters that reflected OTFT device characteristics for ammonia detection were investigated. Significant variations of the turn-on current, intrinsic mobility, and threshold voltage (V-th) were observed while subthreshold swing (S.S.) was almost unchanged to the alteration of ammonia concentration. The OTFT device detected 0.5 similar to 5 ppm concentration ammonia gas at room temperature, which is in the critical range that can distinguish between healthy person and paticents with liver cirrhosis and renal failure. The sensitivity of the device was further enhanced following a simple UV irradiation treatment to modify the functional groups on poly(methyl methacrylate) (PMMA) dielectric layer. Possible interference for ammonia detection such as humidity effect and selectivity among nitrogen, alcohol, carbon dioxide, acetone, methane and ammonia were also examined. We concluded that the proposed pentacene-based OTFT is a promising device for the future application in non-invasive medical diagnoses.
Polymer space-charge-limited transistor as a solid-state vacuum tube triode
(2010-11-29)
Chao, Yu-Chiang
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Ku, Ming-Che
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Tsai, Wu-Wei
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Zan, Hsiao-Wen
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Meng, Hsin-Fei
We report the construction of a polymer space-charge-limited transistor (SCLT), a solid-state version of vacuum tube triode. The SCLT achieves a high on/off ratio of 3 x 10(5) at a low operation voltage of 1.5 V by using high quality insulators both above and below the grid base electrode. Applying a greater bias to the base increases the barrier potential, and turns off the channel current, without introducing a large parasitic leakage current. Simulation result verifies the influence of base bias on channel potential distribution. The output current density is 1.7 mA/cm(2) with current gain greater than 1000. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3513334]
Polymer space-charge-limited transistor as a solid-state vacuum tube triode
(2010-11-29)
Chao, Yu-Chiang
;
Ku, Ming-Che
;
Tsai, Wu-Wei
;
Zan, Hsiao-Wen
;
Meng, Hsin-Fei
We report the construction of a polymer space-charge-limited transistor (SCLT), a solid-state version of vacuum tube triode. The SCLT achieves a high on/off ratio of 3 x 10(5) at a low operation voltage of 1.5 V by using high quality insulators both above and below the grid base electrode. Applying a greater bias to the base increases the barrier potential, and turns off the channel current, without introducing a large parasitic leakage current. Simulation result verifies the influence of base bias on channel potential distribution. The output current density is 1.7 mA/cm(2) with current gain greater than 1000. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3513334]
Reduction of defect formation in amorphous indium-gallium-zinc-oxide thin film transistors by N2O plasma treatment
(2013-11-28)
Jhu, Jhe-Ciou
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Chang, Ting-Chang
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Chang, Geng-Wei
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Tai, Ya-Hsiang
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Tsai, Wu-Wei
An abnormal sub-threshold leakage current is observed at high temperature in amorphous indium-gallium-zinc-oxide thin film transistors (a-IGZO TFTs). This phenomenon occurs due to a reduced number of defects in the device's a-IGZO active layer after the device has undergone N2O plasma treatment. Experimental verification shows that the N2O plasma treatment enhances the thin film bonding strength, thereby suppressing the formation of temperature-dependent holes, which are generated above 400 K by oxygen atoms leaving their original sites. The N2O plasma treatment devices have better stability performance than as-fabricated devices. The results suggest that the density of defects for a-IGZO TFTs with N2O plasma treatment is much lower than that in as-fabricated devices. The N2O plasma treatment repairs the defects and suppresses temperature-dependent sub-threshold leakage current. (C) 2013 AIP Publishing LLC.
Solution-Processed Vertical Organic Transistors Fabricated by Nanoimprint Lithography
(2013-02-01)
Wu, Yang-Kai
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Huang, Jian-Hao
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Tsai, Wu-Wei
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Chen, Yung-Pin
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Lin, Shih-Chieh
In this letter, we demonstrate the first vertical-channel organic transistor using nanoimprint technology to produce a base electrode with high-density nanometer pores to well control the channel current vertically flowing through the pores. The aspect ratios of nanopores, which determine the switching performance of the vertical transistor, are greatly enhanced by transferring the nanostructure to the underlying layers. Without pore accumulation, a low leakage current can be achieved. The vertical transistor delivers an ON current of 0.35 mA/cm(2) and an ON/OFF current ratio of around 3000 at 1.8 V. The results prove the feasibility to produce low-voltage organic transistors over a large area with potentially low production cost.
Vertical polymer phototransistor featuring photomultiplication due to base-field shielding
(2011-01-31)
Zan, Hsiao-Wen
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Tsai, Wu-Wei
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Meng, Hsin-Fei
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物理研究所
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光電工程學系
We introduce a vertical polymer phototransistor with low operational voltage (-1.5 V). A blended polymer layer with both acceptor and donor materials was used as a channel material in the vertical space-charge-limited transistor. Under illumination, we obtained external quantum efficiency (EQE) as high as 360% at 620 nm. We propose the effects of base-field shielding as a means to explain high EQE. This proposition has been supported by two-dimensional simulation of the device. (C) 2011 American Institute of Physics. [doi:10.1063/1.3552714]