Gate Voltage Dependence Ultrahigh Sensitivity WS₂ Avalanche Field-Effect Transistor.

Recently, WS2 has been considered a promising photodetector material due to its benefits of atomic thickness, easily customized single-crystal van der Waals heterostructure, and efficient photon absorption. However, the photosensitivity obtained from the WS2 photodetector is still unsatisfactory. Therefore, this article proposes a WS2-based high sensitivity field-effect transistor (FET) based on avalanche multiplication. Under 532-nm illumination, WS2 FET has ultralow dark current ($10^{-{12}}$ A), high responsivity (74 A/W), and high detectivity ($1.45\times 10^{{13}}$ Jones). In addition, the avalanche breakdown voltage of the device is reduced by employing graphene as an electrode. Because the height of the Schottky barrier can be reduced by replacing the Au electrode with a graphene electrode, the lower Schottky barrier can result in higher electric field intensity in the WS2 channel. Meanwhile, the unique transfer and output characteristics are observed in WS2 FET with graphene electrode. The inherent mechanisms are discussed, considering the Fermi-level tenability of graphene flakes and ambipolar transport properties of WS2. These results open a promising door to realize the WS2 FET with low power consumption and ultrahigh photoresponsivity, which will be ideal for high-performance photodetectors. [ABSTRACT FROM AUTHOR]