Origin of Electrical Instabilities in Self-Aligned Amorphous In–Ga–Zn–O Thin-Film Transistors

This paper examined the performance and bias stability of amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) with a self-aligned coplanar structure. The activation energy barrier responsible for the positive bias thermal stress (PBTS)-induced instability of the a-IGZO TFTs with low oxygen loadings can be attributed to the migration of cation interstitial defects. However, the IGZO TFTs with high oxygen loadings could not be explained by the existing defect model. The first-principle calculation indicates that the cation vacancy, such as V
_In
, with the hydrogen incorporation plays an important role in determining the PBTS-dependent degradation of the threshold voltage.