Self-powered broadband photodetection enabled by facile CVD-grown MoS₂/GaN heterostructures

Achieving self-powered photodetection without biasing is a notable challenge for photodetectors. In this work, we demonstrate the successful fabrication of large-scale van der Waals epitaxial molybdenum disulfide (MoS₂) on a p-GaN/sapphire substrate using a straightforward chemical vapor deposition (CVD) technique. Our research primarily centers on the characterization of these photodetectors produced through this method. The MoS₂/GaN heterojunction photodetector showcases a broad and extensive photoresponse spanning from ultraviolet A (UVA) to near-infrared (NIR). When illuminated by a 532 nm laser, its self-powered photoresponse is characterized by a rise time (τ_r) of ∼18.5 ms and a decay time (τ_d) of ∼123.2 ms. The photodetector achieves a responsivity (R) of ∼0.13 A W⁻¹ and a specific detectivity (D*) of ∼3.8 × 10¹⁰ Jones at zero bias. Additionally, while utilizing a 404 nm laser, the photodetector reaches a maximum R and D* of ∼1.7 × 10⁴ A/W and ∼1.6 × 10¹³ Jones, respectively, at V_b = 5 V. The operational mechanism of the device can be explained by the diode characteristics involving a tunneling current in the presence of reverse bias. The exceptional performance of these photodetectors can be attributed to the pristine interface between the CVD-grown MoS₂ and GaN, providing an impeccably clean tunneling surface. Additionally, our investigation has unveiled that MoS₂/GaN heterostructure photodetectors, featuring MoS₂ coverage percentages spanning from 20% to 50%, exhibit improved responsivity capabilities at an external bias voltage. As a result, this facile CVD growth technique for MoS₂ photodetectors holds significant potential for large-scale production in the manufacturing industry.