Modeling of a-Si:H TFT I-V Characteristics in the Forward Subthreshold Operation
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.
Cite this version of the work
Lei Zhu (2005). Modeling of a-Si:H TFT I-V Characteristics in the Forward Subthreshold Operation. UWSpace. http://hdl.handle.net/10012/868