Visible to near-infrared photodetector based on SnSe₂/WSe₂heterojunction with potential application in artificial...

Two-dimensional (2d) transition-metal dichalcogenides (TMDCs) are promising candidate materials for developing next generation nano optoelectronic devices, due to their strong interaction with light. In addition, the free of surface dangling bonds makes it possible to stacking any different types of 2D TMDCs together to form heterojunctions with desirable band structures for various applications. However, most of the 2D TMDCs are bipolar or strong unipolar n-type doped, while very few of them show weak p-type doping, which severely affects the performance of the formed heterojunctions. In this work, we fabricated a SnSe₂/WSe₂heterojunction of type II band alignment with a small bandgap of ∼0.1 eV, which is ideally for developing optoelectronic devices responsible to a broad light spectrum. N₂O plasma treatment is applied to enhance the p-type doping of both WSe₂and SnSe₂, which results in the increased on-off ratio of n-type SnSe₂by 50 times and the hole mobility of WSe₂by 527 times. The WSe₂/SnSe₂heterostructure also achieves a decent performance as a p-n junction, which exhibits photo responsivity of 450 mA W^-1and 133 mA W^-1for 700 nm visible light and 1600 nm infrared light, respectively, without any gate or source-drain bias, showing great photovoltaic effect. Moreover, the heterojunction shows great promise as an artificial visual neuron, which can differentiate the dark, visible and infrared light illumination conditions by applying a series of electrical pulses through the back-gate electrode.