Browsing by Author "Yang, Chung-Yi"

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Abnormal hump in capacitance-voltage measurements induced by ultraviolet light in a-IGZO thin-film transistors
(2017-01-09)
Tsao, Yu-Ching
;
Chang, Ting-Chang
;
Chen, Hua-Mao
;
Chen, Bo-Wei
;
Chiang, Hsiao-Cheng
This work demonstrates the generation of abnormal capacitance for amorphous indium-gallium-zinc oxide (a-InGaZnO4) thin-film transistors after being subjected to negative bias stress under ultraviolet light illumination stress (NBIS). At various operation frequencies, there are two-step tendencies in their capacitance-voltage curves. When gate bias is smaller than threshold voltage, the measured capacitance is dominated by interface defects. Conversely, the measured capacitance is dominated by oxygen vacancies when gate bias is larger than threshold voltage. The impact of these interface defects and oxygen vacancies on capacitance-voltage curves is verified by TCAD simulation software. Published by AIP Publishing.
Effect of mechanical-strain-induced defect generation on the performance of flexible amorphous In-Ga-Zn-O thin-film transistors
(2016-12)
Liao, Po-Yung
;
Chang, Ting-Chang
;
Su, Wan-Ching
;
Chen, Yu-Jia
;
Chen, Bo-Wei
In this study, we investigate the effect of mechanical strain on the performance of flexible amorphous In-Ga-Zn-O (a-.InGaZnO) thin-film transistors. Drain current-gate voltage (ID-VG) and capacitance-voltage (C-V) transfer curves are measured to analyze the degradation behavior. The ID-VG characteristic exhibits a clear negative shift under mechanical strain regardless of the tension or compression state. In addition, the C-V characteristic curves show a leftward shift with extra distortion or stretching out under mechanical strain. This indicates that InGaZnO generates additional defects under this mechanical strain, a phenomenon that can be attributed to the generation of mechanical-strain-induced oxygen vacancies on the flexible a-InGaZnO TFTs. (C) 2016 The Japan Society of Applied Physics.
Effects of Repetitive Mechanical Bending Strain on Various Dimensions of Foldable Low Temperature Polysilicon TFTs Fabricated on Polyimide
(2016-08)
Chen, Bo-Wei
;
Chang, Ting-Chang
;
Hung, Yu-Ju
;
Huang, Shin-Ping
;
Liao, Po-Yung
This letter investigates the effect of repeated uniaxial mechanical stress on bias-induced degradation behavior in polycrystalline thin-film transistors (TFTs). After 100 000 iterations of channel-width-direction mechanical compression, serious threshold voltage degradation and an abnormal hump are observed. Simulation indicates that the strongest mechanical stress occurs at both sides of the channel edge, between the polycrystalline silicon and gate insulator. Since these stress points produce oxide traps in the gate insulator, the degradation of threshold voltage shift and parasitic current path can be attributed to electron trapping at these intense mechanical stress points. In addition, the degradation becomes serious with diminishing TFT size.
Impact of repeated uniaxial mechanical strain on flexible a-IGZO thin film transistors with symmetric and asymmetric structures
(2017-06-26)
Liao, Po-Yung
;
Chang, Ting-Chang
;
Su, Wan-Ching
;
Chen, Bo-Wei
;
Chen, Li-Hui
This letter investigates repeated uniaxial mechanical stress-induced degradation behavior in flexible amorphous In-Ga-Zn-O thin-film transistors (TFTs) of different geometric structures. Two types of via-contact structure TFTs are investigated: symmetrical and UI structure (TFTs with Iand U-shaped asymmetric electrodes). After repeated mechanical stress, I-V curves for the symmetrical structure show a significant negative threshold voltage (VT) shift, due to mechanical stress-induced oxygen vacancy generation. However, degradation in the UI structure TFTs after stress is a negative VT shift along with the parasitic transistor characteristic in the forward-operation mode, with this hump not evident in the reverse-operation mode. This asymmetrical degradation is clarified by the mechanical strain simulation of the UI TFTs. Published by AIP Publishing.
Investigation of Hydration Reaction-Induced Protons Transport in Etching-Stop a-InGaZnO Thin-Film Transistors
(2015-10-01)
Jhu, Jhe-Ciou
;
Chang, Ting-Chang
;
Chang, Kuan-Chang
;
Yang, Chung-Yi
;
Chou, Wu-Ching
In this letter, protons (hydrogen ions, H+ ions) transport-induced unstable transient electrical characteristics were found and studied in the etching-stop-layer in via-contact-type amorphous-indium-gallium-zinc-oxide thin-film transistors (a-IGZO TFTs) for the first time. By applying negative gate bias stress, more water molecules will be absorbed on the surface of the passivation layer, and thus the transmission of net protons in the etching-stop will increase. The proton transport model established in this letter can effectively analyze the a-IGZO TFTs instability using the threshold voltage (VT) determined from the current-voltage measurements, and which is unstable in a moist environment.
The effect of device electrode geometry on performance after hot-carrier stress in amorphous In-Ga-Zn-O thin film transistors with different via-contact structures
(2017-05-15)
Liao, Po-Yung
;
Chang, Ting-Chang
;
Chen, Yu-Jia
;
Su, Wan-Ching
;
Chen, Bo-Wei
In this letter, the effects of hot carriers on amorphous In-Ga-Zn-O thin film transistors (TFTs) of different geometric structures were investigated. Three types of via-contact structure TFTs are used in this experiment, defined as source-drain large (SD large), source-drain normal (SD normal), and fork-shaped. After hot-carrier stress, the I-V curves of both SD normal and fork-shaped TFTs with U-shaped drains show a threshold voltage shift along with the parasitic transistor characteristic in the reverse-operation mode. Asymmetrical degradation is exhibited in an ISE-TCAD simulation of the electric field, which shows the distribution of hot electrons injected into the etch-stop layer below the redundant drain electrode. Published by AIP Publishing.