Binary-ternary transition metal chalcogenides interlayer coupling in van der Waals type-II heterostructure for visible-infrared photodetector with efficient suppression dark currents

Ternary two-dimentional (2D) materials exhibit diverse physical properties depending on their composition, structure, and thickness. Through forming heterostructures with other binary materials that show similar structure, there can be numerous potential applications of these ternary 2D materials. In this work, we reported the structure of few-layer CrPS₄ by X-ray diffraction, transmission electron microscope, and electron-density distribution calculation. We also demonstrated a new application of the CrPS₄/MoS₂ heterobilayer: visible-infrared photodetectors with type-II staggered band alignment at room temperature. The response of the heterostructure to infrared light results from a strong interlayer coupling that reduces the energy interval in the junction area. Since the intrinsic bandgap of individual components determines wavelengths, the decrease in energy interval allows better detection of light that has a longer wavelength. We used photoluminescence (PL) spectroscopy, Kelvin probe force microscopy (KPFM) under illumination, and electrical transport measurements to verify the photoinduced charge separation between the CrPS₄/MoS₂ heterostructures. At forward bias, the device functioned as a highly sensitive photodetector, as the wavelength-dependent photocurrent measurement achieved the observation of optical excitation from 532 to 1,450 nm wavelength. Moreover, the photocurrent caused by interlayer exciton reached around 1.2 nA at 1,095 nm wavelength. Our demonstration of the strong interlayer coupling in the CrPS₄/MoS₂ heterostructure may further the understanding of the essential physics behind binary-ternary transition metal chalcogenides heterostructure and pave a way for their potential applications in visible-infrared devices.