Mechanism analysis of large-scale heteroepitaxial diamond solar-blind ultraviolet photodetectors with ultralow dark current

Diamond serves as an ideal platform for solar-blind ultraviolet (SBUV) photodetectors owing to its ultra-wide bandgap, high carrier mobility, and radiation hardness. However, the absence of large, cost-effective bulk substrates has impeded large-scale diamond fabrication. This study reports the first demonstration of an SBUV metal–semiconductor–metal (MSM) photodetector based on heteroepitaxial single-crystal diamond grown on Ir/Al₂O₃ substrates. The film, produced via epitaxial lateral overgrowth (ELO), exhibits a low etch pit density and a sharp diamond Raman peak, thereby confirming high film quality. Photoluminescence analysis indicates the presence of only weak NV⁰/NV⁻ and SiV⁻ centers within the film, further affirming its crystalline integrity. Additionally, MSM devices with Ti/Pt interdigitated electrodes on top of the fabricated diamond film demonstrate an exceptionally low dark current (8.6 × 10⁻¹⁴ A at 20 V), a UV/visible rejection ratio of approximately 10³, and a responsivity reaching 0.34 A W⁻¹ at 220 nm (equivalent to an external quantum efficiency of approximately 192 %), with a detectivity of 5.4 × 10¹² Jones. Moreover, the carrier transport mechanisms under varying temperature conditions are analyzed to gain insight into optimization directions. These findings substantiate the potential of heteroepitaxial diamond as a promising wafer-scale platform for SBUV detection and offer mechanistic insights to inform future defect-reduction strategies aimed at advancing high-speed, high-reliability optoelectronic devices.