  Two-dimensional (2D) heterointerfaces often provide extraordinary carrier
transport as exemplified by superconductivity or excitonic superfluidity.
Recently, double-layer graphene separated by few-layered boron nitride
demonstrated the Coulomb drag phenomenon: carriers in the active layer drag the
carriers in the passive layer. Here, we propose a new switching device
operating via Coulomb drag interaction at a graphene/MoS2 (GM) heterointerface.
The ideal van der Waals distance allows strong coupling of the interlayer
electron-hole pairs, whose recombination is prevented by the Schottky barrier
formed due to charge transfer at the heterointerface. This device exhibits a
high carrier mobility (up to ~3,700 cm^2V^-1s^-1) even at room temperature,
while maintaining a high on/off current ratio (~10^8), outperforming those of
individual layers. In the electron-electron drag regime, graphene-like
Shubnikov-de Haas oscillations are observed at low temperatures. Our Coulomb
drag transistor could provide a shortcut for the practical application of
quantum-mechanical 2D heterostructures at room temperature.
