A Substrate Bias Effect on Recovery of the Threshold Voltage Shift of Amorphous Silicon Thin-Film Transistors

概要

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Hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) were fabricated on a flexible stainless-steel (SS) substrate. The stability of the a-Si:H TFT is a key issue for active matrix organic light-emitting diodes (AMOLEDs). The drain current decreases because of the threshold voltage shift ($\Delta V_{\text{TH}}$) during OLED driving. A negative voltage at a floated gate can be induced by a negative substrate bias through a capacitor between the substrate and the gate electrode without additional circuits. The negative voltage biased at the SS substrate can recover $\Delta V_{\text{TH}}$ and reduced drain current of the driving TFT. The $V_{\text{TH}}$ of the TFT increased by 2.3 V under a gate bias of $+15$ V and a drain bias of $+15$ V at 65 °C applied for 3,500 s. The $V_{\text{TH}}$ decreased by $-2.3$ V and the drain current recovered 97% of its initial value under a substrate bias of $-23$ V at 65 °C applied for 3,500 s.
2007-07-15