Enhancement of the Photoresponse of Monolayer MoS₂ Photodetectors Induced by a Nanoparticle Grating
2020
Li, Jialu | Nie, Changbin | Sun, Feiying | Tang, Linlong | Zhang, Zijing | Zhang, Jiandong | Zhao, Yuan | Shen, Jun | Feng, Shuanglong | Shi, Haofei | Wei, Xingzhan
Photodetectors based on two-dimensional (2D) materials such as monolayer MoS₂ are attractive because they can be directly integrated into the 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 the 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, photothermal 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.
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