-homojunction achieved with oxygen plasma-treatment for broadband photodetector applications*

2D transition metal dichalcogenides have shown significant potential for developing future nanoscale optoelectronic devices, among them, bulk tungsten diselenide (WSe₂) with an indirect bandgap (1.2 eV) is a promising material for optoelectronic applications due to its tunable energy bands, fast charge transfer, and strong optical absorption. Here, we demonstrate the fabrication of WSe₂ lateral pn-homojunction via oxygen (O₂) plasma-doping for high-performance broadband photodetector applications. The WSe₂ pn-homojunction photodetectors display higher photoresponsivities of 250 mA/W and 2000 mA/W, EQE of 97 % and 420 %, and detectivity of 7.7 × 10⁹ Jones and 7.2 × 10¹⁰ Jones for visible (520 nm) and near IR (852 nm) laser illuminations, respectively at V_g = 0V and V_d = 1V. The O₂ plasma-doping enables an effective charge generation and separations at the junctions upon the laser illuminations and resulting in superior optoelectronic properties which aid us in the development of lateral pn-homojunction as promising broadband photodetectors.