Origin of High Current and Illumination Stress Instability in Self-Aligned a-InGaZnO Thin Film Transistors With Al 2 O 3 as High-κ Gate Dielectric

This paper analyzes the effect of high current under illumination stress (HCIS) in self-aligned amorphous indium gallium zinc oxide transistors with Al ₂ O ₃ as high- $\kappa $ gate dielectric. A negative parallel threshold voltage $({V}_{T}$ ) shift with the appearance of hysteresis $(\Delta {V}_{{hys}})$ is observed after HCIS. In contrast to the double ionized oxygen vacancy ( $\text{V}_{\text O}^{\text 2+}$ ) theory, a peroxide donor theory based on ${ab~ initio}$ calculations is proposed to explain the degradation. Several methods are carried out to support the mechanism, including $\Delta {V}_{{hys}}$ generation, stress recovery behavior and capacitance-voltage ${(C-V)}$ measurements. A linear dependence between initial ${V}_{T}$ and negative ${V}_{T}$ shift is observed that further supports the peroxide theory. This work highlights the importance of evaluating the HCIS for oxide base semiconductor devices.