Near‐Ideal Schottky Junction Photodetectors Based on Semimetal‐Semiconductor Van der Waals Heterostructures

Schottky junction barrier is promising to suppress dark current in photodetectors by blocking the tunneling electrons. Due to the Fermi pinning effect, designing the Schottky barrier with a conventional 3D metal/2D semiconductor interface is challenging. Here, it is shown that a 2D semimetal‐semiconductor van der Waals Schottky junction can be utilized to design the near‐ideal Schottky barrier for the high Ion/Ioff ratio photodetectors. It is demonstrated that the experimental barrier height (≈467 meV) of the 1T′‐MoTe2/WS2 Schottky junction can largely follow the Schottky‐Mott rule by effectively resolving the Fermi pinning effect. Such increased barrier height suppresses the thermionic emission (TE) and the tunneling of the electrons. However, for the photo‐generated electron‐hole pairs with the higher energy case, holes cannot be prevented, while most of the electrons with the higher energy can also be easily transferred. The 1T′‐MoTe2/WS2/1T′‐MoTe2 photodetector exhibits the dark current density of 5 × 10−13 A µm−1, a light on/off ratio of 106, a responsivity of 30 A W−1, and a detectivity of 1.82 × 1014 Jones. Modulated Schottky barrier height is adopted to construct a self‐powered 1T′‐MoTe2/WS2/Au photodetector. Here, the 2D semimetal‐semiconductor van der Waals Schottky junction can be utilized to design the near‐ideal Schottky barrier for the high Ion/Ioff ratio photodetectors. Such Schottky junction photodetector can exhibit a dark current density of 5 × 10−13 A µm−1 with an Ion/Ioff ratio of 106. The self‐powered photodetector can also be constructed by designing the barrier height.