Insulating Y2O3 modification for high-performance TiO2 ultraviolet photodetectors

A metal-insulator-semiconductor (MIS) ultraviolet photodetector (UVPD) with a Y 2 O 3 insulating film inserted between TiO 2 and the Au electrode as a passivation layer has been successfully fabricated, aiming to address the critical bottlenecks of the relatively low light-to-dark current ratio and excessively high dark current in single TiO 2 -based devices. In this work, the insulator Y 2 O 3 is introduced as a multifunctional modification layer. The Y 2 O 3 film passivates the oxygen vacancy defects on the TiO 2 surface and acts as a physical barrier layer to block the interference of the external environment on TiO 2 . Under dark conditions, the insulating layer serves as a natural barrier that effectively blocks majority carriers and suppresses leakage paths, leading to a substantial reduction in dark current. Under UV illumination, the thin insulating Y 2 O 3 layer between Au and TiO 2 can optimize the metal–semiconductor contact and effectively screen the Schottky barrier at the interface, enabling efficient electron injection via trap-assisted tunneling, which enhances the photocurrent compared with that of single TiO 2 devices. Benefiting from the above synergistic design, under illumination from a light source covering the entire ultraviolet band, the device exhibits a photocurrent of 110 μA, a dark current reduced to 0.16 nA, and a photo-to-dark current ratio as high as 6.87 × 10 5 at a bias of 5 V, along with a responsivity of 90.02 A/W and a specific detectivity of 7.7 × 10 14 Jones under 270 nm UV illumination. This work reveals the unique potential of insulating oxide/semiconductor interface engineering in constructing high-performance photoconductive detectors, and provides a new pathway for low-cost, high-sensitivity UV detection.