Modeling of a-Si:H TFT I-V Characteristics in the Forward Subthreshold Operation

Electrical & Computer Engineering;thin-film transistor;device modeling;subthreshold operation

Zhu, Lei

University of Waterloo

关键词: Electrical & Computer Engineering;    thin-film transistor;    device modeling;    subthreshold operation;   

Others  :  https://uwspace.uwaterloo.ca/bitstream/10012/868/1/l2zhu2005.pdf

瑞士|英语

来源: UWSPACE Waterloo Institutional Repository

【 摘 要 】

The hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) are widely used as switching elements in LCD displays and large area matrix addressed senor arrays.In recent years, a-Si:H TFTs have been used as analog active components in OLED displays. However, a-Si:H TFTs exhibit a bias induced metastability.This problem causes both threshold voltage and subthreshold slope to shift with time when a gate bias is applied.These instabilities jeopardize the long-term performance of a-Si:H TFT circuits.Nevertheless a-Si:H TFTs show an exponential transfer characteristic in the subthreshold region.Moreover, the typical power consumptions for TFTs in the subthreshold region are in the order of nano-watts, thus making them suitable for low power design.For these reasons, a-Si:H TFT I-V characteristics in the forward subthreshold operation are investigated.First, we have derived the static and dynamic models of a-Si:H TFT in the forward subthreshold region.Second, we have verified our theoretical models with experimental results.Third, we have proven that a-Si:H TFT experiences no subthreshold slope degradation or threshold voltage shift in the forward subthreshold operation.Finally, we have studied a-Si:H TFT current mirror circuit applications.Measurements regarding the fidelity of current matching in the forward subthreshold region have been performed, and results are shown.