A Two-Stage Degradation Model of p-Channel Low-Temperature Poly-Si Thin-Film Transistors Under Positive Bias Temperature Stress

Positive-bias temperature-stress-induced degradation in p-channel poly-Si thin-film transistors is investigated. Two-stage degradation behavior is observed. In the first-stage degradation, on-state current (I_ON) initially increases associated with a positive threshold voltage (V_th) shift and is then followed by a gradual I_ON decrease. In the second stage, V_th shifts to the negative, and I_ON significantly degrades. A comprehensive physical model is proposed to clarify the two-stage degradation behavior. The first-stage degradation is attributed to electron trapping and detrapping, whereas the second-stage degradation is dominated by positive charge generation.