Optoelectronic performance characterization of MoS2 photodetectors for low frequency sensing applications

The specific advantages of implementing MoS2 and other layered semiconductors for optoelectronic biosensing and other relevant photodetection applications remain unclear. In this work, we investigate the photoresponsivity and noise characteristics of in-plane MoS2 photodetectors. This work indicates that MoS2 photodetectors exhibit lower noise equivalent power (NEP) and detectivity (D*) in comparison with commercial CdS photodetectors. In addition, the low-frequency NEP and D* values of MoS2 photodetectors exhibit a prominent dependence on the MoS2 photoactive layer thickness. We have identified the optimal MoS2 thickness in the range of 8–30 nm. We also study the photoresponse characteristics of optimized MoS2 photodetectors at several different wavelengths that are important for clinical colorimetry assays. Such an optimized photodetector shows a maximum photoresponsivity of 164.3 A/W and a minimum NEP of 3.99 × 10−17 W/Hz1/2 (and a D* of 5.01 × 1010 J) with relative variance less than 14%. This work provides a useful guideline for optimizing the photoresponse characteristics of MoS2-based optoelectronic devices, which is critical to practical low-frequency optoelectronic biosensing applications.