High Number of Transport Modes: A Requirement for Contact Resistance Reduction to Atomically Thin Semiconductors

Electrical contacts to atomically thin 2-D semiconductors are considered as the hindering aspect of electronic devices based on these materials. The high resistance of such contacts stems from their Schottky nature in contrast to the desired low-resistance Ohmic contacts. This issue of Schottky contacts is thus one of the major inhibitors to the integration of 2-D materials into mainstream technology. In this work, we explore contact resistance (R-C) to atomically thin 2-D semiconductors in terms of the injected current through the Schottky barrier (SB) by using the Landauer-Buttiker formalism as well as experimental measurements and technology computer aided design (TCAD) simulations. We show that the SB height and width, which are determined by the metal- semiconductor interface and the number of charge carriers in the semiconductor channel, respectively, affect R-C when it is relatively high (R-C > 1 k omega middot mu m). However, the number of transport modes for carrier injection is the limiting factor for aggressive R-C lowering (R-C < 1 k omega middot mu m), even for near -zero SB height. Our results show that to reduce R-C below 100 omega middot mu m, large number of transport modes are required, which can be accomplished through raising the number of channel carriers above 5middot10(13) cm(-2) by means of heavy doping or gating. Our conclusions offer insight for future contact engineering and can explain recently published state-of-the-art results.

Automated summary

This article explores the issue of contact resistance in atomically thin 2-D semiconductors, which hinders the integration of these materials into mainstream technology. The resistance is found to be influenced by the height and width of the Schottky barrier, as well as the number of transport modes for carrier injection. To reduce the contact resistance, a large number of transport modes can be achieved by increasing the number of channel carriers through heavy doping or gating.