P-type laser-doped WSe ₂ /MoTe ₂ van der Waals heterostructure photodetector

Abstract

Abstract Van der Waals heterostructures (vdWHs) based on two-dimensional (2D) materials are being studied extensively for their prospective applications in photodetectors. As the pristine WSe 2 /MoTe 2 heterostructure is a type I (straddling gap) structure, it cannot be used as a photovoltaic device theoretically, although both WSe 2 and MoTe 2 have excellent photoelectric properties. The Fermi level of p-doped WSe 2 is close to its valence band. The p-doped WSe 2 /MoTe 2 heterostructure can perform as a photovoltaic device because a built-in electric field appears at the interface between MoTe 2 and p-doped WSe 2 . Here, a 633 nm laser was used for scanning the surface of WSe 2 in order to obtain the p-doped WSe 2 . x-ray photoelectron spectroscopy (XPS) and electrical measurements verified that p-type doping in WSe 2 is produced through laser treatment. The p-type doping in WSe 2 includes substoichiometric WO x and nonstoichiometric WSe x . A photovoltaic device using p-doped WSe 2 and MoTe 2 was successfully fabricated. The band structure, light-matter reactions, and carrier-transport in the p-doped WSe 2 /MoTe 2 heterojunction were analyzed. The results showed that this photodetector has an on/off ratio of ≈10 4 , dark current of ≈1 pA, and response time of 72 μ s under the illumination of 633 nm laser at zero bias ( V ds = 0 V). The proposed p-doping method may provide a new approach to improve the performance of nanoscale optoelectronic devices.