Photodetection Mechanisms and Ultraviolet–Visible Imaging Characteristics of High-Detectivity Broadband Metal–Semiconductor–Metal Photodetector Arrays on Wafer-Scale Monolayer MoS₂

The discovery of an intrinsic direct bandgap in single-layer MoS₂ has revealed significant potential for advancements in optoelectronic and photonic applications. This study aims to explore this potential by developing a high-performance Ni/Au metal-semiconductor-metal photodetector on wafer-scale epitaxially grown MoS₂. The quality of the monolayer MoS₂ film was verified using various techniques, including Raman, photoluminescence (PL), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Results showed a high photoresponse of 2.06 and 0.68 A/W under 350 and 650 nm light illumination, respectively, at a 10 V reverse bias, along with an ultralow dark current measured in picoamps. These results indicate a low noise level and high photo-to-dark current rejection ratios of 5.45 × 10⁴ and 3.41 × 10⁴ under 350 and 650 nm illumination, respectively. The photodetector exhibited a maximum detectivity of 5.1 × 10¹⁶ cm Hz^1/2 W^-1 at 5 V under 350 nm of UV illumination, and the quantum efficiency surpassed 100% when the reverse bias voltage exceeded 3 V, demonstrating gain manifestation within the device. The dominance of a trap-assisted photoconductive gain mechanism was suggested by the power law exponent and the temporal characteristics observed. UV and visible imaging capabilities were also demonstrated using a "MoS2"-printed shadow mask and a single metal-semiconductor-metal (MSM) photodetector. This study highlights the superior photoimaging capabilities of the MoS₂ MSM photodetector, offering substantial contributions to the field of optoelectronics and suggesting practical applications in photonic devices.