In a related strategy, graphene has been reported as a material for the thermoelectric management of nanoscale devices due to its high thermal conductivity , low heat capacity , and unique hot carrier cooling dynamics . After excitation, the photogenerated charge carriers in graphene can thermalize themselves via carrier scattering with a temperature of hundreds of Kelvins higher than the lattice, inducing excess electrical heat . With its gapless band structure and vdW property, combining graphene and TMDCs to construct heterostructure devices targets the utilization of these hot electrons for photodetection at telecom wavelengths with highly efficient hot carrier injection, reduced wasted heat, and low dark currents. The charge carrier dynamics in graphene/TMDC heterostructures have been extensively investigated via all-optical pump-probe methods, where hot carrier transfer or injection from graphene to adjacent layers over the Schottky barrier is reported at the picosecond time scale . Terahertz and all-optical pump-probe studies showed that the injected hot electrons can be trapped by the defects in the TMDC or recycled via electron-phonon interactions from the heterostructure. This way, the injected carrier lifetime could be extended to nanoseconds, which enabled the harvesting of hot carriers over realistic device lengths. This is an important prerequisite for solving the trade-off between high response speed and high responsivity in such a device. However, a demonstration of this principle in actual devices via optical pump-photocurrent probe experiments have not been reported so far.