van der Waal’s heterostructure at the Schottky-Mott limit

Recently, the Schottky-Mott (SM) limit has been studied through measurements on many metal-semiconductor junctions with various metals [1]. Here, we probe the SM limit using a single, gate-tunable, hexagonal boron nitride encapsulated graphene-WSe₂-graphene heterostructure. One-dimensional edge contacts are made to the graphene and buried split-gates are used to separately tune the electrical properties each graphene-WSe₂ junction. By making one graphene-WSe₂ junction Ohmic, we perform electrical measurements of the Schottky barrier (SB) formed in the other junction. Electrical measurements of the SB show striking agreement with the ideal-diode equation, with over thirteen decades of drain current modulation via the gate voltage. Arrhenius activation energy measurements reveal one-to-one electrical control of the SB height by the gate voltage. These measurements indicate a stark absence of Fermi-level pinning at the graphene-WSe₂ interface, resulting in a tunable SM limited heterojunction. Our findings are of broad significance, enabling fundamental studies of the SM limit and the ability to make superior electrical contact to two-dimensional materials.

[1] Y. Liu, J. Guo, E. Zhu, L. Liao, S.-J. Lee, M. Ding, I. Shakir, V. Gambin, Y. Huang, and X. Duan, Nature 557, 696 (2018).