Mechanism of a-InGaZnO Thin Film Transistors Degradation Under Negative Gate-Pulse Stress

The degradation of amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) under high-frequency negative gate-pulsed stress was investigated. The results indicate that the degradation of a-IGZO TFTs shifts positively depending on the number of pulse repetitions rather than the accumulated stress time, which contrasts with the effects observed under low-frequency gate pulses. Notably, it is observed for the first time that the degree of degradation is determined by the pulse rising time(tr)and is independent of the pulse falling time(tf), a steeper pulsetrleads to more severe degradation. Based on degradation behaviors, we propose that the degradation mechanism under negative gate-pulse stress can be attributed to hot-carriers injection into the gate-oxide near the vicinity of source/drain electrodes and channel. Simulation-based quantitative analysis of transient lateral/vertical electric field and electron concentration at the vicinity verifies the proposed degradation model.