Recovery behaviors in n-channel LTPS-TFTs under DC stress

In this paper, the degradation and recovery behaviors of polycrystalline silicon (poly-Si) thin film transistor (TFT) under direct current (dc) stress were investigated. Under positive or negative gate stress with a drain bias stress, the similar degradation and recovery behaviors were observed. The similar recovery is a limited one compared to the degradation before removing the bias stress. It is determined that hot-carrier effect is the key degradation mechanism under the positive or negative gate stress condition. The devices without drain bias stress appear no recovery behavior after removing the stress, which implies that the hot-carrier degradation is mainly because of the lateral electrical field rather than the vertical electrical field. In contrast to the degradation caused by hot-carrier effect, the degradation caused by the vertical gate electrical field cannot be recovered after removing the stress.