Effect of post-deposition treatment on electrical properties of solution-processed a-IGZO Schottky diodes

Abstract

The fabrication of solution-processed electronic devices based on amorphous In-Ga-Zn-O (a-IGZO) requires high-temperature post-deposition annealing to activate IGZO layers and minimize impurities. Deep-ultraviolet (DUV) treatment can reduce the post-deposition annealing temperature when manufacturing a-IGZO thin-film transistors. Here, we investigate the effect of thermal annealing and DUV treatment in a nitrogen and ozone atmosphere on the properties of vertical thin-film Pt-IGZO-Cu Schottky diodes based on spin-coated a-IGZO. The DUV treatment in nitrogen allowed reducing the process temperature to 200 °C. A defect-induced hysteresis was observed on the current-voltage characteristics of as-fabricated Schottky diodes. The values of rectification ratio and barrier height were higher and the values of ideality factor were lower upon the backward bias sweep. It is assumed that the hysteresis behavior is caused by the presence of trap states in the semiconductor layer or at the Schottky interface. A trap density of 108 cm-2 to 1011 cm-2 was deduced from the current-voltage characteristics. The defect-induced hysteresis effect could be suppressed by depositing an Al2O3 layer and applying an additional thermal treatment of the whole diode structure.