Highly Responsive Ultrathin GaS Nanosheet Photodetectorson Rigid and Flexible Substrates.

Thefirst GaS nanosheet-based photodetectors are demonstrated onboth mechanically rigid and flexible substrates. Highly crystalline,exfoliated GaS nanosheets are promising for optoelectronics due tostrong absorption in the UV–visible wavelength region. Photocurrentmeasurements of GaS nanosheet photodetectors made on SiO2/Si substrates and flexible polyethylene terephthalate (PET) substratesexhibit a photoresponsivity at 254 nm up to 4.2 AW–1and 19.2 AW–1, respectively, which exceeds thatof graphene, MoS2, or other 2D material-based devices.Additionally, the linear dynamic range of the devices on SiO2/Si and PET substrates are 97.7 dB and 78.73 dB, respectively. Bothsurpass that of currently exploited InGaAs photodetectors (66 dB).Theoretical modeling of the electronic structures indicates that thereduction of the effective mass at the valence band maximum (VBM)with decreasing sheet thickness enhances the carrier mobility of theGaS nanosheets, contributing to the high photocurrents. Double-peakVBMs are theoretically predicted for ultrathin GaS nanosheets (thicknessless than five monolayers), which is found to promote photon absorption.These theoretical and experimental results show that GaS nanosheetsare promising materials for high-performance photodetectors on bothconventional silicon and flexible substrates. [ABSTRACT FROM AUTHOR]