In this paper, the behavior of the low-temperature polycrystalline-silicon (LTPS) thin film transistors (TFTs) during X-ray irradiation and gate bias voltage (VG) simultaneously is analyzed. Both n-type and p-type LTPS TFTs show negative shifts of threshold voltage under same dose of X-ray irradiation, regardless of the VG polarity, while the field effect mobility of n-type LTPS TFT keeps fairly well. The degradation of subthreshold swing is attributed to the interface states, which can be repaired by 300 °C annealing. A model is proposed to explain the results for different VG, and verified by changing the thickness of the gate oxide. More irradiation-induced holes are trapped by the far defects owing to the electric field. This study can be helpful to develop more stable devices or circuits for the application of X-ray image sensors.
- Gate bias
- Gate insulator
- Low-temperature polycrystalline silicon (LTPS)
- Thin-film transistor (TFT)