Browsing by Author "Yeh, Shan"

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Effects of X-ray Irradiation on the Noise Behavior of Amorphous Indium-Gallium-Zinc-Oxide TFTs
(2020-01-17)
Tai, Ya-Hsiang
;
Yeh, Shan
;
Chen, Zheng-Chi
;
Chang, Ting-Chang
;
電機學院
In this paper, the response of low-frequency noise under and after the X-ray irradiation for amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs) is analyzed. With fixed irradiation dose, the noise stays the same regardless of the TFT under and after X-ray irradiation. The noise mechanism is analyzed to be mainly the carrier mobility fluctuation. The coincidence of the noise of TFTs under and after X-ray irradiation further confirms that there is no direct relation between X-ray irradiation and the noise behavior. The mechanism of the positive charge trapping in the oxide layer under X-ray for the threshold voltage (V-th) shift of the TFT does not affect its noise behavior. With more stable and larger SNR by 20 dB than low-temperature polycrystalline-silicon (LTPS) TFT, a-IGZO TFT is believed to be a more suitable device for applying to X-ray active pixel sensing circuits. (c) 2020 The Electrochemical Society ("ECS"). Published on behalf of ECS by IOP Publishing Limited.
LTPS Active Pixel Circuit With Threshold Voltage Compensation for X-Ray Imaging Applications
(2019-10-01)
Tai, Ya-Hsiang
;
Lin, Chi-Hao
;
Yeh, Shan
;
Tu, Cheng-Che
;
Karim, Karim S.
In this article, we proposed a low-temperature poly-silicon (LTPS) active pixel sensor (APS) circuit with threshold voltage (V-th) compensation. LTPS thin-film transistors (TFTs) are known to degrade under long-term irradiation and this is quantified. Simulation results and experimental data confirm that the proposed APS circuit compensates the instability of LTPS TFTs and is a promising, high-performance alternative to current amorphous silicon (a-Si) pixel-based X-ray detectors.
Negative threshold voltage shift for LTPS TFTs under x-ray irradiation and gate bias
(2019-09-01)
Tai, Ya-Hsiang
;
Yeh, Shan
;
Chan, Po-Chun
;
Li, Yi-Shen
;
Huang, Shih-Hsuan
In this paper, the behavior of the low-temperature polycrystalline-silicon (LTPS) thin film transistors (TFTs) during x-ray irradiation and gate bias voltage (V-G) simultaneously is analyzed. Both n-type and p-type LTPS TFTs show negative shifts of threshold voltage under same dose of x-ray irradiation, regardless of the V-G polarity, while the field effect mobility of n-type LTPS TFT keeps fairly well. The degradation of subthreshold swing is attributed to the interface states, which can be repaired by 300 degrees C annealing. A model is proposed to explain the results for different V-G, and verified by changing the thickness of the gate oxide. More irradiation-induced holes are trapped by the far defects owing to the electric field. This study can be helpful to develop more stable devices or circuits for the application of x-ray image sensors.
Total-Dose Effect of X-ray Irradiation on Low-Temperature Polycrystalline Silicon Thin-Film Transistors
(2020-06-01)
Tai, Ya-Hsiang
;
Yeh, Shan
;
Huang, Shih-Hsuan
;
Chang, Ting-Chang
;
電機學院
In this paper, the total-dose effect of X-ray irradiation on low-temperature polycrystalline-silicon (LTPS) thin film transistors (TFTs) is studied. Experiments under different conditions, including fixed intensity, fixed time, fixed total dose, short shot with different frequencies and high/low intensity for short/long time were performed and analyzed. With an increase of the irradiation dose, the threshold voltage (Vth) shifts negatively, the subthreshold swing (S.S.) degrades and the field effect mobility decreases owing to positive trapped charges and interface traps. All magnitude of negative shifts of (Vth), (S. S.) and field effect mobility for LTPS TFTs are well correlated to the total accumulated dose. The results are consistent with (Vth) shift due to trapped holes and the interface traps for mobility.
Total-Dose Effect of X-ray Irradiation on Low-TemperaturePolycrystalline Silicon Thin-Film Transistors (vol 41, pg 864, 2020)
(2020-09-01)
Tai, Ya-Hsiang
;
Yeh, Shan
;
Huang, Shih-Hsuan
;
Chang, Ting-Chang
;
電機學院
In The above article [1], the Acknowledgment was deleted in error. Therefore, the Acknowledgment is added below. This change had no influence on the discussion and conclusions in the article.