Rhenium Diselenide (ReSe₂) Near-Infrared Photodetector: Performance Enhancement by Selective p-Doping Technique

In this study, a near-infrared photodetector featuring a high photoresponsivity and a short photoresponse time is demonstrated, which is fabricated on rhenium diselenide (ReSe₂) with a relatively narrow bandgap (0.9-1.0 eV) compared to conventional transition-metal dichalcogenides (TMDs). The excellent photo and temporal responses, which generally show a trade-off relation, are achieved simultaneously by applying a p-doping technique based on hydrochloric acid (HCl) to a selected ReSe₂ region. Because the p-doping of ReSe₂ originates from the charge transfer from un-ionized Cl molecules in the HCl to the ReSe₂ surface, by adjusting the concentration of the HCl solution from 0.1 to 10 m, the doping concentration of the ReSe₂ is controlled between 3.64 × 10¹⁰ and 3.61 × 10¹¹ cm^-2. Especially, the application of the selective HCl doping technique to the ReSe₂ photodetector increases the photoresponsivity from 79.99 to 1.93 × 10³ A W^-1, and it also enhances the rise and decay times from 10.5 to 1.4 ms and from 291 to 3.1 ms, respectively, compared with the undoped ReSe₂ device. The proposed selective p-doping technique and its fundamental analysis will provide a scientific foundation for implementing high-performance TMD-based electronic and optoelectronic devices.