Effects of Oxygen Content and Thermal Annealing on Sputtered a-IGZO Schottky Diodes

Effects of oxygen content during sputtering of amorphous In-Ga-Zn-O (a-IGZO) and post-deposition thermal annealing on the properties of vertical thin-film Schottky diodes were investigated. Increase of the oxygen content in the Ar/O2 mixture from 0 to 20% led to lower current densities. At the same time higher oxygen content enhanced the Ion/Ioff ratio of the Schottky diodes without post-treatment. The current-voltage characteristics exhibited a shift of the current minimum point depending on the bias sweep direction for the devices fabricated at 11.76% and 20% of oxygen. The post-deposition thermal annealing in air was found to improve the Ion/Ioff ratio with an optimum annealing temperature of 200°C although the effect depended on the initial oxygen content. Ideality factor and barrier height were calculated for all fabricated devices. Schottky diodes on glass based on IGZO sputtered at 3.23 - 6.25% of oxygen with Ion/Ioff ratio of 2.6•106 – 1.6•107 at ±1 V, ideality factor of 1.3 - 1.5, and barrier height of 0.62 - 0.67 eV were obtained after annealing at 200°C.