In contrast to the intensive studies on thin-film transistors based on indium gallium zinc oxide (IGZO), the research on IGZO-based diodes is still very limited, particularly on their behavior and stability under high bias voltages. Our experiments reveal a sensitive dependence of the breakdown voltage of IGZO Schottky diodes on the anode metal and the IGZO film thickness. Devices with an Au anode are found to breakdown easily at a reverse bias as low as −2.5 V, while the devices with a Pd anode and a 200-nm, fully depleted IGZO layer have survived up to −15 V. All diodes are fabricated by radio-frequency magnetron sputtering at room temperature without any thermal treatment, yet showing an ideality factor as low as 1.14, showing the possibility of achieving high-performance Schottky diodes on flexible plastic substrate.

By studying different annealing effects of substrate and anode metal, high-performance Schottky diodes based on InGaZnO (IGZO) film have been realized. It is observed that a suitable thermal annealing of the SiO 2 /Si substrate significantly improves the diode performance. In contrary, annealing of the Pd anode increases surface roughness, leading to degradation in the diode performance. As such, by only annealing the substrate but not the anode, we are able to achieve an extremely high rectification ratio of 7.2 × 10 7 , a large barrier height of 0.88 eV, and a near unity ideality factor of 1.09. The diodes exhibit the highest performance amongst IGZO-based Schottky diodes reported to date where IGZO layer is not annealed.The capacitance vs. voltage measurements indicate that the surface roughness is correlated with the trap state density at the Schottky interface.

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Recently, Indium gallium zinc oxide (InGaZnO or IGZO) has attracted much attention for flexible and transparent electronics, because of its superior electric properties, optical transparency and low processing temperature. In this work, Schottky diodes with a structure of Pd/IGZO/Ti/Au were fabricated by radio‐frequency magnetron sputtering at room temperature without any thermal treatment. The optimised diode with a 66‐nm‐IGZO layer shows an extremely large barrier height (1.02 eV), a very high rectification ratio (> 8.5 × 107), and a close to unit ideality factor (1.23). Our results suggest that Pd and IGZO can form very high quality Schottky contact with a large barrier height, extremely low defects density and high uniformity. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)