Pronounced Optoelectronic Effect in n–n ReS₂ Homostructure

Two-dimensional layered materials have attracted attention for optoelectronic applications owing to their remarkable photonic properties. Here, we report a homojunction device fabricated using n-type ReS2 flakes; the device exhibits p–n diode characteristics. The band structures of 1–5 L ReS2 are theoretically calculated, and the insensitivity of work function to the thickness is experimentally investigated using Kelvin probe force microscopy. The contact resistance and intrinsic mobility of ReS2 field-effect transistors with different thicknesses are evaluated using the Y-function method (YFM). As the thickness of the flakes increases, the contact resistance decreases while the intrinsic mobility increases, leading to a reduction in the threshold voltage. Moreover, the rectifying behavior of a vertical ReS2 (thin)–ReS2 (thick) homostructure is measured at various bias and gate voltages, where the devices exhibit a noticeable rectification ratio of ∼4 × 102 at Vd = 5 V and Vg = 20 V. The ideality factor of the devices is ∼1.16 at Vg = −20 V. In addition, broadband near-infrared (NIR) response of the single-flake homostructure of ReS2 is observed, and it exhibited a responsivity of 170.9 A W–1 at 365 nm. Our study of the ReS2 homostructure leads to the advancement in electronic devices, such as photodetectors, transistors, and photovoltaic cells of new technology.