Correlation of the change in transfer characteristics with the interfacial trap densities of amorphous In–Ga–Zn–O thin film transistors under light illumination

The change in the transfer characteristics of amorphous In–Ga–Zn–O thin film transistors (TFTs) was investigated under light illumination at various wavelengths. The variations in the interfacial trap density (Dit) were also studied using metal-insulator-semiconductor capacitors. The transfer characteristics of the TFTs were dependent on the wavelength of illuminated light. The increase in subthreshold swing observed under light illumination of wavelengths below 550 nm (∼2.3 eV) was confirmed to be related to the increase in Dit near the conduction band edge. This Dit increase is caused by doubly ionized oxygen vacancies (VO2+) that are temporarily generated under light illumination.