Reliability Of A-InGaZnO Thin-Film Transistors Under Negetive Gate Bias And Illumination Stress

In this study,instabilities of amorphous InGaZnO(a-IGZO)thin-film transistors(TFTs)under both negative gate stress(NBS)and negative gate illumination stress(NBIS)are investigated for different stress gate biases(VG),temperatures(T)and light intensities(I)systematically.The degradation behaviors and mechanisms are investigated and analyzed,and a unified degradation model of NBS and NBIS is proposed.Firstly,we study the degradation of a-IGZO TFT under NBS.It's found that there are two kinds of degradation under NBS,namely a continuous negative threshold voltage(Vth)shift which is commonly reported,and the other is rarely reported a two-stage degradation which is a small positive shift followed by a negative shift of VthSecondly,the degradation of a-IGZO TFT under NBIS is investigated.It is found that there are also two kinds of degradation under NBIS which is similar to the degradation under NBS.One notes that the YG and T dependencies are almost the same in both kinds of degradation under NBS and NBIS degradation.In addition,their recovery processes show a great similarity,It strongly suggests that there should be some intrinsic correlation between the NBS and NBIS degradation and underlying mechanisms should be unifiedLastly,a unified model is proposed to explain the NBS and NBIS instabilites of a-IGZO TFTs.In this model,the generated negative charges and ionized oxygen vacancy(Vo2+)at the channel/GI interface respectively are responsible for the positive and negative Vth shift.