Clarifying the 'Oxygen-Defect Principle' That Determines the Performance of Oxide Semiconductor Devices

The operating principle of 'oxygen vacancy defects' that govern oxide semiconductor performance has been revealed for the first time. This discovery is expected to impact process design for thermal treatment and thin-film structure in display and next-generation memory device fabrication. Researchers at UNIST proved through theoretical calculations that the properties of oxygen vacancy defects depend not on how densely atoms are packed in the semiconductor material, but on the distance between metal atoms surrounding the defect. The IGZO material, composed of indium, gallium, zinc, and oxygen, is widely used in thin-film transistors for smartphones and TV screens due to its low-temperature fabrication properties. However, oxygen vacancy defects formed during thin-film manufacturing can destabilize device performance by altering current flow and operating voltage. The team confirmed that device operating voltage and performance change based on whether electrons trapped in the vacancy site remain localized or spread across the thin film. This localization/spread behavior depends on the atomic arrangement around the vacancy, with closer metal atom spacing causing electron localization and increased spacing enabling electron spread across the thin film. The study was published in the ACS journal Chemistry of Materials.