An ultrahigh responsivity UV photodetector enabled by a spatially confined 2D β-Ga2O3/PdSe2 van der Waals heterojunction

Abstract

High-responsivity, solar-blind ultraviolet (UV) photodetectors with ultralow dark currents and exceptional photo-to-dark current ratios are essential for next-generation optoelectronic systems. Despite recent progress, achieving simultaneously high responsivity and stringent spectral selectivity remains a significant challenge. Herein, we demonstrate a breakthrough in solar-blind UV detection through rational design of a van der Waals (vdW) heterojunction comprising spatially confined β-Ga₂O₃ nanosheets and mechanically exfoliated PdSe₂ flakes. The β-Ga₂O₃ nanosheets, synthesized via space-confined CVD, exhibit atomic-level uniformity and superior crystallinity, while the narrow-bandgap PdSe₂ forms a type-II band alignment that drives efficient interfacial charge separation. This engineered heterostructure delivers an ultralow dark current (∼1 pA at 5 V), an extraordinary photo-to-dark current ratio exceeding 10⁶ under 254 nm UV illumination, and a record-high responsivity of 6.17 × 10⁴ A W⁻¹ at a modest UV intensity of 251 µW cm⁻², among the highest reported for solar-blind detectors based on 2D β-Ga₂O₃ heterostructures. This intrinsic wide bandgap of β-Ga₂O₃ ensures strict solar-blind operation (200–400 nm), while the vdW interface minimizes trap-assisted recombination and enhances the carrier extraction efficiency. This work establishes a 2D/2D oxide heterostructure platform and interfacial strategy for high-performance UV photodetection, enabling integrable multifunctional optoelectronics with ultralow detection limits and customized spectral responses.