Degradation of Amorphous Silicon Thin Film Transistors Under Negative Gate Bias Stress

Zhou, Dapeng; Wang, Mingxiang; Zhang, Shengdong

doi:10.1109/ted.2011.2161635

Cited by 12 publications

(6 citation statements)

References 16 publications

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“…As reported in Refs. [8]- [15] in the NBS degradation of poly-TFTs, the shift of the threshold voltage may be affected by both fixed charges in gate oxide and interface states, and it can be expressed as [28,29] − ∆V th = ∆V it + ∆V ox = q∆N it /C ox − q∆N ox /C ox (5) and…”

Section: Influence On I-v I-v I-v Characteristicsmentioning

confidence: 99%

“…As switching elements and peripheral circuits, lowtemperature polysilicon thin film transistors (poly-Si TFTs) have been widely used in high-performance active matrix liquid crystal displays (AMLCD) and active matrix organic light emitting diodes (AMOLED). [1,2] During its application in the display field, poly-Si TFTs may be exposed to various environments, such as temperature, bias stress, etc., [3][4][5][6] thereby changing the characteristics of poly-Si TFTs and further affecting the performance of peripheral circuits. [7] Therefore, its reliability is the key issue for circuit application of TFT.…”

Section: Introductionmentioning

confidence: 99%

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Negative gate bias stress effects on conduction and low frequency noise characteristics in p-type poly-Si thin-film transistors*

Han¹,

Liu²,

Liu³

et al. 2019

Chinese Phys. B

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The instability of p-channel low-temperature polycrystalline silicon thin film transistors (poly-Si TFTs) is investigated under negative gate bias stress (NBS) in this work. Firstly, a series of negative bias stress experiments is performed, the significant degradation behaviors in current–voltage characteristics are observed. As the stress voltage decreases from −25 V to −37 V, the threshold voltage and the sub-threshold swing each show a continuous shift, which is induced by gate oxide trapped charges or interface state. Furthermore, low frequency noise (LFN) values in poly-Si TFTs are measured before and after negative bias stress. The flat-band voltage spectral density is extracted, and the trap concentration located near the Si/SiO2 interface is also calculated. Finally, the degradation mechanism is discussed based on the current–voltage and LFN results in poly-Si TFTs under NBS, finding out that Si–OH bonds may be broken and form Si* and negative charge OH− under negative bias stress, which is demonstrated by the proposed negative charge generation model.

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Section: Influence On I-v I-v I-v Characteristicsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Negative gate bias stress effects on conduction and low frequency noise characteristics in p-type poly-Si thin-film transistors*

Han¹,

Liu²,

Liu³

et al. 2019

Chinese Phys. B

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show abstract

“…Therefore, suppressing the degradation of the blue photo TFT is important to avoid malfunctions of the WPCG structure. Generally, the degradation of a-Si:H TFTs is related to the gate-source voltage during long-term operation [20], so Fig. 4 plots the changes in the photocurrent that occur when the blue photo TFTs are driven using different gate-source voltages under long-term stress by illumination.…”

Section: Device Characteristicsmentioning

confidence: 99%

Long-Term Behavior of Hydrogenated Amorphous Silicon Thin-Film Transistors Covered With Color Filters for Use in Optical Sensors

et al. 2019

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This work investigates the long-term behavior of photo thin-film transistors (TFTs) that are covered with color filters and based on hydrogenated amorphous silicon (a-Si:H) technology. Based on the electrical characteristics and the optical responses of these TFTs as measured under different stress conditions, a new method for driving a photo TFT with a negative gate-source voltage is proposed to suppress the degradation of the photocurrent. The effectiveness of the newly proposed method is verified using our previously developed white-light photocurrent gating (WPCG) structure, the measurement of photocurrents, and the established models of red, green, and blue photo TFTs. An accelerated lifetime test of the fabricated circuit was carried out at 70 • C and under the illumination of ambient light for 504 hours, demonstrating that the proposed method improves the long-term reliability of optical sensors.INDEX TERMS Hydrogenated amorphous silicon thin-film transistor, long-term reliability, optical sensor.

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“…Besides, the processes of α-Si:H TFTs were relatively mature so they were still competitive devices. Therefore, there were many literatures focused on the reliability of α-Si:H TFTs, which supposed that two main mechanisms causing the deterioration of α-Si:H TFTs stressed by electrical biases (5)(6)(7).…”

Section: Introductionmentioning

confidence: 99%

(Digital Presentation) Instability of α-Si:H TFTs under Simultaneous Ultraviolet Light Illumination and Different Bias Stresses

Liu¹,

Hung²,

Huang³

2022

ECS Trans.

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The threshold voltage degradation and recovery phenomena of the α-Si:H TFTs stressed by DC or AC biases under with or without UV light illumination are investigated. For the negative DC bias stress, the threshold voltage shift of the stressed α-Si:H TFTs measured in the reverse sweep mode is smaller than that in the forward sweep mode, but the threshold voltage recovery is opposite, owing to the different increment of subthreshold swing of the α-Si:H TFTs after stressing. For the AC biases stresses, there are no significant difference of threshold voltage shift between the stressed α-Si:H TFTs measured by forward sweep and reverse sweep modes due to the less increment of subthreshold swing of the α-Si:H TFTs after stressing. There are more threshold voltage degradation but less recovery of the α-Si:H TFTs stressed by lower AC frequency with the higher negative bias in a cycle than those stressed by higher AC frequency.

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Degradation of Amorphous Silicon Thin Film Transistors Under Negative Gate Bias Stress

Cited by 12 publications

References 16 publications

Negative gate bias stress effects on conduction and low frequency noise characteristics in p-type poly-Si thin-film transistors*

Negative gate bias stress effects on conduction and low frequency noise characteristics in p-type poly-Si thin-film transistors*

Long-Term Behavior of Hydrogenated Amorphous Silicon Thin-Film Transistors Covered With Color Filters for Use in Optical Sensors

(Digital Presentation) Instability of α-Si:H TFTs under Simultaneous Ultraviolet Light Illumination and Different Bias Stresses

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