Suspended MoS2 Photodetector Using Patterned Sapphire Substrate.

The introduction of patterned sapphire substrates (PSS) has been regarded as an effective method to improve the photoelectric performance of 2D layered materials in recent years. Molybdenum disulfide (MoS2 ), an intriguing transition metal 2D materials with splendid photoresponse owing to a direct-indirect bandgap transition at monolayer, shows promising optoelectronics applications. Here, a large-scale, continuous multilayer MoS2 film is prepared on a SiO2 /Si substrate and transferred to flat sapphire substrate and PSS, respectively. An enhanced dynamic distribution of local electric field and concentrated photon excitons across the interface between MoS2 and patterned sapphire substrates are revealed by the finite-difference time-domain simulation. The photoelectric performance of the MoS2 /PSS photodetector is improved under the three lasers of 365, 460, and 660 nm. Under the 365 nm laser, the photocurrent increased by 3 times, noise equivalent power (NEP) decreases to 1.77 × 10-14 W/Hz1/2 and specific detectivity (D*) increases to 1.2 × 1010 Jones. Meanwhile, the responsivity is increased by 7 times at 460 nm, and the response time of the MoS2 /PSS photodetector is also shortened under three wavelengths. The work demonstrates an effective method for enhancing the optical properties of photodetectors and enabling simultaneous detection of broad-spectrum emissions.

High-Performance MoS2 Photodetectors Prepared Using a Patterned Gallium Nitride Substrate.

Strain-adjusting the band gap of MoS2 using patterned substrates to improve the photoelectric performance of MoS2 has gradually become a research hotspot in recent years. However, there are still difficulties in obtaining high-quality two-dimensional materials and preparing photodetectors on patterned substrates. To overcome this, a continuous multilayer MoS2 film was transferred to a patterned gallium nitride substrate (PGS) for the fabrication of photodetectors, and density functional theory calculations showed that the band gap of the MoS2 film increased and that the electron effective mass decreased due to the introduction of PGS. In addition, finite difference time domain simulation showed that the electric field in the MoS2 area on the PGS is enhanced compared with that on the flat gallium nitride substrate due to the enhanced light scattering effect of the PGS. The photoresponse of the MoS2/PGS photodetector at 460 nm was also enhanced, with Iph increasing by 5 times, R increasing by 2 times, NEP decreasing to 3.88 × 10-13 W/Hz1/2, and D* increasing to 5.6 × 108 Jones. Our research has important guiding significance in adjusting the band gap of MoS2 and enhancing the photoelectric performance of MoS2 photodetectors.