Degradation Behaviors Of Flexible TFTs Under DC Gate Bias Stress

Degradation behaviors of flexible and conventional p-channel LTPS TFTs under DC PBS and NBS are investigated comparatively in this study.Conventional TFTs we used in experiments shows typical degradation behaviors.Flexible TFTs before lift-off show worst reliability under both PBS and NBS due to lower fabrication temperature.After laser lift-off process,flexible TFTs show much different degradation behaviors.In PBS,flexible TFTs after lift-off exhibit two-stage degradation with positive(1_?shift in the first-stage and negative(1_?shift in the second-stage,which is explained as a competition between electron trapping and P-F emission.In NBS,minor negative(1_?shift is found for flexible TFTs after lift-off when comparing to devices before lift-of and even conventional ones.Positive shift of transfer curve in deep subthreshold region at room temperature is observed,which is not appearing at higher temperature.This study indicates that substrate detachment affects the reliability of flexible TFTs by affecting gate dielectric and causing defect generation inside and being more likely to trap negative charge.The deformation of flexible sample after lift-off origins from built-in stress mismatch but the IV curve and reliability change after lift-off are mainly owing to gate oxide affection.For flexible display development using the similar process,researchers should care about the reliability of devices after substrate delamination especially,together with transfer characteristics change before and after lift-off.Moreover,in our study,it is great to find flexible TFTs after lift-off show good reliability comparable to conventional TFTs under both PBS and NBS condition.Reliability of flexible a-IGZO TFTs is also investigated and significant difference is observed for a-IGZO TFT before lift-off and after lift-off.