Fundamentals of low-resistive 2D-semiconductor metal contacts: an ab-initio NEGF study

Abstract

Metal contacts form one of the main limitations for the introduction of 2D materials in next-generation scaled devices. Through ab-initio simulation techniques, we shed light on the fundamental physics and screen several 2D and 3D top and side contact metals. Our findings highlight that a low semiconducting-metal contact resistance can be achieved. By selecting an appropriate 2D metal, we demonstrate both ohmic or small Schottky barrier top and side contacts. This leads to a contact resistance below 100 Ωμm and good device drive performance with currents in ON state up to 1400 μA/μm, i.e., reduced by a mere 25% compared to a reference with perfect ohmic contacts, provided a sufficiently high doping concentration of 1.8×1013 cm−2 is used. Additionally, we show that this doping concentration can be achieved through electrostatic doping with a gate. Finally, we perform a screening of possible 2D–3D top contacts. Finding an ohmic 2D–3D contact without a Schottky barrier has proven difficult, but it is shown that for the case of intermediate interaction strength and a limited Schottky barrier, contact resistances below 100 Ωμm can be achieved.