heterostructures*

Two-dimensional (2d) nano-electronics, plasmonics, and emergent phases require clean and local charge control, calling for layered, crystalline acceptors or donors. Here, we demonstrate that the large work function narrow-band Mott insulator RuCl₃ enables modulation doping of exfoliated single and bilayer graphene, chemical vapor deposition (CVD) grown graphene and WSe₂, and molecular beam epitaxy (MBE) grown EuS. OurRaman measurements show high hole densities 3*10¹³cm^-2 in mlg RuCl₃ heterostructures and 6*10¹³cm^-2 in bilayer graphene (blg) RuCl3 heterostructures. In addition, our study suggest photovoltage devices, charge transfer control via twist angle, and charge transfer through hexagonal boron nitride (hBN).