Suspended few-layered GaS photodetector with high responsivity and fast response speed

Abstract The layered GaS has attracted much attention in the field of photodetection recently because of its considerable responsivity (∼A/W) caused by the high quantum yields, while its slow response speed (∼ ms) due to the low carrier mobility limits its practical applications. Here, by separating a few-layered GaS (∼15 nm) with its substrate to prepare a device with the typical suspended architecture, we trade off its responsivity with speed for the first time. A responsivity of ∼103 A/W and a switch time of ∼ μs are achieved simultaneously in a wide UV-vis range (300-628 nm), which exceeds that of the most current 2D material-based photodetectors. The excellent mechanical stiffness of layered GaS avoids the interface scattering and trap caused by the contacting with substrate or its own deformation. This is beneficial to the significant improvement of carrier mobility and fully activating the intrinsic properties of GaS. Combined with the comparative experiments and band theory analysis, this assertion is confirmed and the photoconductance effect is determined to play a dominant role. These results show a promising strategy for improving the performance of GaS photodetector, especially providing references for its future integrated devices.