Half-Valley Ohmic Contact and Contact-Limited Valley-Contrasting Current Injection

TL;DR

This paper introduces a novel contact mechanism in valleytronics using FVSC/graphene heterostructures, enabling gate-tunable valley-polarized current injection for potential valleytronic devices.

Contribution

It proposes a half-valley Ohmic contact concept and develops a theory for contact-limited valley-contrasting current injection, demonstrating its application in valleytronic devices.

Findings

Contact-limited valley-contrasting current injection can produce tunable valley polarization.

A device concept of valleytronic barristor with high polarization efficiency.

Feasible electrostatic gating conditions achieve sizable current on/off ratios.

Abstract

Two-dimensional (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 we generalize the concept of metal/semiconductor (MS) contact into the realm of valleytronics. We propose a half-valley Ohmic contact 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. We develop a theory of contact-limited valley-contrasting current injection and demonstrate that such transport mechanism can produce gate-tunable valley-polarized injection current. Using RuCl$_2$/graphene heterostructure as an example, we illustrate a device concept of valleytronic barristor 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.