Half‐Valley Ohmic Contact: Contact‐Limited Valley‐Contrasting Current Injection

The 2D ferrovalley semiconductor (FVSC) with spontaneous valley polarization offers an exciting material platform for probing Berry phase physics. How FVSC can be incorporated in valleytronic device applications, however, remain an open question. Here, the concept of metal/semiconductor (MS) contact into the realm of valleytronics is generalized. A half‐valley Ohmic contact is proposed based on FVSC/graphene heterostructure, where the two valleys of FVSC separately forms Ohmic and Schottky contacts with those of graphene, thus allowing current to be valley‐selectively injected through the ‘Ohmic’ valley while being blocked in the ‘Schottky’ valley. A theory of contact‐limited valley‐contrasting current injection is developed and such transport mechanism can produce gate‐tunable valley‐polarized injection current. Using RuCl2/graphene heterostructure as an example, a device concept of valleytronic barristor is illustrated, where high valley polarization efficiency and sizable current on/off ratio, can be achieved under experimentally feasible electrostatic gating conditions. These findings uncover contact‐limited valley‐contrasting current injection as an efficient mechanism for valley polarization manipulation, and reveals the potential of valleytronic MS contact as a functional building block of valleytronic device technology. The concept of metal/semiconductor into the realm of valleytronics is generalized. Half‐valley Ohmic contact is proposed, which allows contact‐limited valley‐contrasting current injection to be achieved. A device concept, known as valleytronic barristor, is demonstrated, showcasing high valley polarization efficiency and current on/off switching under practical electrostatic gating.