Ultra-high Photoresponsivity in Suspended Metal-Semiconductor-Metal Mesoscopic Multilayer MoS 2 Broadband Detector from UV-to-IR with Low Schottky Barrier Contacts
The design, fabrication, and characterization of ultra-high responsivity photodetectors based on mesoscopic multilayer MoS 2 is presented, which is a less explored system compared to direct band gap monolayer MoS 2 that has received increasing attention in recent years. The device architecture is comprised of a metal-semiconductor-metal (MSM) photodetector, where Mo was used as the contact metal to suspended MoS 2 membranes. The photoresponsivity R was measured to be ~1.4 × 10 4 A/W, which is > 10 4 times higher compared to prior reports, while the detectivity D* was computed to be ~2.3 × 10 11 Jones at 300 K at an optical power P of ~14.5 pW and wavelength λ of ~700 nm. In addition, the dominant photocurrent mechanism was determined to be the photoconductive effect (PCE), while a contribution from the photogating effect was also noted from trap-states that yielded a wide spectral photoresponse from UV-to-IR (400 nm to 1100 nm) with an external quantum efficiency (EQE) ~10 4 . From time-resolved photocurrent measurements, a decay time τ d ~ 2.5 ms at 300 K was measured from the falling edge of the photogenerated waveform after irradiating the device with a stream of incoming ON/OFF white light pulses.