Modified Threshold Voltage Shift Model in a-Si:H TFTs Under Prolonged Gate Pulse Stress

The threshold voltage (V_T) instability of hydrogenated amorphous silicon thin film transistor under constant gate bias stress has been examined and modeled as a stretched-exponential equation previously. However, the V_T shift (Delta V_T) characteristic under prolonged gate pulsed stress, which also occurs in practical circuit operation, has not been well modeled so far. In this letter, we compared the V_T shift property with existing models under gate pulse stress. For Delta V_T under prolonged stress, we found inaccuracies in the previous models and subsequently proposed a modified model, which can be applied to estimate V_T shift correctly for prolonged pulse stress of various duty ratios.