High-κ Lanthanide Oxide Enabled pA-Scale Background Current Suppression in ZnO Single-Crystal Ultraviolet Photodetectors

Abstract

Ultraviolet (UV) detection, owing to its excellent noise immunity, is widely used in ultra-high-voltage power grid corona monitoring, fire warning, missile tracking, and medical imaging. Zinc oxide (ZnO), a wide-bandgap semiconductor, shows strong potential due to its inherent UV spectral selectivity. However, intrinsic unintentional doping defects in ZnO single crystals lead to a high background carrier concentration, which causes excessive leakage current in ZnO-based devices and limits their performance in detecting weak UV signals. In this work, by introducing a high-κ lanthanide oxide heterostructure, we achieved a pA-scale background current in a device based on a natural ZnO single crystal. A polycrystalline ytterbium oxide (Yb₂O₃) thin film was sputter-deposited on ZnO single crystals to form a Yb₂O₃/ZnO heterojunction, which reduced the dark current by 8–9 orders of magnitude in the fabricated Au/Yb₂O₃/ZnO metal-insulator-semiconductor (MIS)-type photodetector. The heterojunction device exhibits a notable photoresponse under 365 nm illumination, with a response time of 188.9/153.4 ms and a photocurrent-to-dark-current ratio (PDCR) of approximately 250. These results demonstrate that high-κ lanthanide oxide can be effectively used to construct heterostructures for ZnO single-crystal devices, providing a promising pathway toward developing filter-free and highly integrated ZnO single-crystal UV imaging systems.