Enhancement of the Photoresponse of Monolayer MoS2 Photodetectors Induced by a Nanoparticle Grating.

Photodetectors based on two-dimensional (2D) materials such as monolayer MoS2 are attractive because they can be directly integrated into current metal-oxide semiconductor (CMOS) structures. Unfortunately, such devices suffer from low responsivity due to low absorption by the monolayer MoS2. Combining MoS2 with plasmonic nanostructures is an alternative solution for enhancing the absorption of the 2D semiconductor and this can drastically increase the photoresponsivity of the corresponding photodetector. Herein, a device incorporating a grating-patterned nanoparticle structure is fabricated using traditional photolithography together with an annealing step. We demonstrate that this new structure leads to a strong enhancement in the photocurrent due to coupling of the MoS2 to localized surface plasmons in the nanoparticle grating. Compared to a simple Au nanoparticle array, the nanoparticle grating structure generates a 100% increase in optical absorption. Thus, under 532 nm illumination, the composite nanoparticle grating/monolayer MoS2 integrated photodetector shows a 111-fold increase in the photocurrent compared to the same device in the absence of nanoparticles. The gateless responsivity can be up to 38.57 A/W and a specific detectivity of 9.89×109 Jones is realized. Moreover, photo-thermal flux derivations indicate that, in addition to the expected increase due to light-generated carrier multiplication, the thermal effects of plasmons provide a significant contribution to the photocurrent enhancement.