Origin of High Current and Illumination Stress Instability in Self-Aligned a-InGaZnO Thin Film Transistors With Al2O3 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 Al2O3 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 (V-O(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.