Modulation doping in van der Waals materials: Transport characteristics of α-RuCl3/graphene heterostructures

Recently, we discovered that the layered Mott insulator α-RuCl₃ can induce a large population of holes of order few 10¹³ cm^-2 in graphene and other layered materials, demonstrating its capability as a strong 2d crystalline acceptor. Graphene doped by contact with α-RuCl₃ shows the highest reported transport mobilities at such large carrier densities due to the clean and uniform interface between the materials. Unexpectedly, we find that the charge transfer persists to a lesser degree even when α-RuCl3 and graphene are separated by an insulating spacer layer up to a few nm thick, achieving a separation of the charge origin from the active conducting layer that is analogous to modulation doping in epitaxially-grown semiconductors. Thus α-RuCl₃ enables a degree of control to selectively dope specific layers within a van der Waals heterostructure. It can also be readily patterned to engineer a custom potential landscape. In this talk, we will discuss transport characteristics of α-RuCl₃/graphene heterostructures including details of modulation doping through layers of hexagonal boron nitride and aluminum oxide, as well as prototype devices that showcase advantages of using α-RuCl₃ as a 2d crystalline acceptor.