Tunable p-Type Doping in Large-Scale MoS₂ Films Realized by Selective-Area Gd Deposition for Self-Powered Broadband Fast Photoresponse

Self-powered ultralow energy consumption broadband optoelectronic devices based on two-dimensional (2D) semiconductor p–n junctions have emerged as a promising candidate for next-generation smart optosensors owing to the superior photoresponse driven by the intrinsic built-in electric field. However, efficient p-type doping remains a critical challenge for constructing high-performance devices. In this work, we developed a well-controllable doping procedure by ultrahigh vacuum (UHV) selective-area deposition and solid-state reaction, which has been applied in the tunable p-type doping of rare-earth metal Gd in large-scale MoS₂ films. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and Kelvin probe force microscopy (KPFM) characterizations confirm uniform and effective doping in the selected area, with a 0.29 eV downward shift of the Fermi level induced by Gd substitution. Two terminal photodetection devices have been fabricated on the Gd-doped MoS₂ lateral p–n homojunctions by using the shadow-mask-assisted patterned electrode deposition that guarantees atomically clean interfaces. Optoelectronic transport measurement under illumination of varying wavelengths revealed robust self-powered broadband photoresponse, featuring an open-circuit voltage of 38 mV at zero bias, as well as high responsivity (5.42 A/W) and detectivity (8.06 × 10¹¹ Jones) from the visible to near-infrared wavelengths range (300–1270 nm). In addition, the response speed has been improved by 3 orders of magnitude (from 10⁴ ms to 20–50 ms) owing to the carrier recombination rate and mobility being enhanced by doping. Our work provides insights for the future advanced optoelectronic sensors of various 2D layered materials.