Browsing by Author "Tu, Cheng-Che"

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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.