Browsing by Author "Lin, Sung-Chun"

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An Energy-Band Model for Dual-Gate-Voltage Sweeping in Hydrogenated Amorphous Silicon Thin-Film Transistors
(2019-06-01)
Chen, Guan-Fu
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Chen, Hong-Chih
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Chang, Ting-Chang
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Huang, Shin-Ping
;
Chen, Hua-Mao
This paper clarifies the correct transmission mechanism, misattributed in the previous research, of a hydrogenated amorphous silicon thin-film transistor (a-Si:H TFT) device. Complete drain current-gate voltage (I-D-V-G) transfer characteristics including the forward and backward gate sweeps (gate voltage carried out in the OFF-state -> on-state and the ON-state -> OFF-state) are performed, and the physics models of an energy-band schematic are clearly explained. This paper reveals that the I-D-V-G curve stretch-out behavior of the subthreshold region is due to the leakage of the Poole-Frenkel region. At the Poole-Frenkel regions, electrons transfer to the drain terminal, and holes remain in the valance band of the a-Si:H bulk. The remaining holes represent the positive voltage and cause the electron barrier height lowering. This causes an increase in subthreshold current of the subthreshold region. Finally, three experiments are performed to prove the correctness of these models, and the a-Si TFTs device improvement methods will be proposed to enhance the stability and performance of product of the a-Si TFTs.
Drain-Induced-Barrier-Lowing-Like Effect Induced by Oxygen-Vacancy in Scaling-Down via-Contact Type Amorphous InGaZnO Thin-Film Transistors
(2018-01-01)
Yang, Chung-I.
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Chang, Ting-Chang
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Liao, Po-Yung
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Chen, Li-Hui
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Chen, Bo-Wei
This investigation considers a method to ameliorate drain induced barrier lowing behavior in amorphous-indium-gallium-zinc-oxide thin-film transistors. The Vth is found to shift negatively when increasing the ID-VG measurement condition VD from 0.1 to 15 V. The current-voltage curves show that this degradation is caused by the effective channel length (L-eff) being shorter than the mask channel length (L). Using the transmission line method to extract Leff, we discover that the degradation will be completely suppressed by an annealing treatment. As a result, the degradation mechanism of shorter channel length a-IGZO thin film transistors is due to oxygen-vacancies which are located between the channel and the source/drain junction.
Investigating degradation behaviors induced by hot carriers in the etch stop layer in amorphous InGaZnO thin film transistors with different electrode materials and structures
(2017-12-31)
Yang, Chung-I
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Chang, Ting-Chang
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Chen, Bo-Wei
;
Chou, Wu-Ching
;
Liao, Po-Yung
This work investigates the hot carrier effect in via-contact type amorphous indium gallium zinc oxide thin film transistors with various source/drain materials and structures. According to previous research, the redundant drain electrode plays an important role in hot carrier stress-induced degradation, which leads to carrier-trapping in the etch stop layer between the active layer and the redundant drain electrode. Hot carrier stress has different influences on device characteristics, depending on materials and structure. Hot carrier stress causes more electron trapping in the etch stop layer below the redundant drain electrode in the presence of smaller source/drain metal work function or a longer redundant drain electrode. To further verify the mechanisms of the degradation behavior, the barrier height for Fowler-Nordheim-tunneling is extracted by a fitting charge trapping model. It is found that the barrier height for Fowler-Nordheim-tunneling is different for different source/drain materials.
Investigating degradation behaviors induced by mobile Cu ions under high temperature negative bias stress in a-InGaZnO thin film transistors
(2017-09-25)
Chiang, Hsiao-Cheng
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Chang, Ting-Chang
;
Liao, Po-Yung
;
Chen, Bo-Wei
;
Tsao, Yu-Ching
This letter investigates the effect of negative bias temperature stress (NBTS) on amorphous InGaZnO4 thin film transistors with copper electrodes. After 2000 s of NBTS, an abnormal subthreshold swing and on-current (I-on) degradation is observed. The recovery of the Id-Vg curve after either annealing or positive bias temperature stress suggests that there are some native mobile copper ions in the active layer. Both the existence of copper and the degradation mechanism can be confirmed by AC stress with different frequencies and by transmission electron microscope energy-dispersive X-ray spectroscopy analysis. Published by AIP Publishing.