One of the most important challenges for the development of information technology is the large heat dissipation caused by long-distance data transmission and fast signal conversion in high densities . A major source for such electrical heat is the generation of hot electrons, which refers to high-temperature carriers beyond the thermal equilibrium with the lattice . If this electrical heat could be effectively harnessed, heat dissipation would be reduced and the power conversion efficiency of the device simultaneously enhanced . A promising strategy in this respect is the photo-thermionic effect. Briefly, if the photon energy of the optical signal is higher than the Schottky barrier between a metal and a semiconductor, the photogenerated hot electrons in the metal can be extracted and injected into the adjacent semiconductor after their thermalization . This photoelectric effect enables a sub-bandgap photoresponse at telecom wavelengths in 2D TMDCs without sacrificing response speed. However, due to the relatively weak light absorption by the metal, the conventional metal-semiconductor-metal structure requires an integration into silicon waveguides to enhance the hot electron injection efficiency , which makes the device configuration sophisticated and limits the response to certain wavelengths.