Investigation of tow-step electrical degradation behavior in a-InGaZnO thin-film transistors with Sm₂O₃ gate dielectrics

We investigate the electrical stress-induced instability in amorphous indium-gallium-zinc oxide (a-IGZO) thin-film transistors (TFTs) with Sm ₂O₃ gate dielectrics. Tow-step electrical degradation behavior in Sm₂O₃ a-IGZO TFT devices was found under high gate and drain voltage stress during 1000 s. A typical small positive shift followed by an unusual negative shift of threshold voltage is characterized in our TFT devices. We believe that the positive shift of the threshold voltage is due to charge trapping in the gate dielectric and/or at the channel/dielectric interfaces, while the negative shift of threshold voltage can be attributed to the generation of extra electrons from oxygen vacancies in the a-IGZO channel. We suggested that the amount of oxygen vacancies and the quality of the high-κ gate dielectric probably affect the degradation behavior of a-IGZO TFT devices.