Metallization-Induced Quantum Limits of Contact Resistance in Graphene Nanoribbons with One-Dimensional Contacts

Graphene has attracted a lot of interest as a potential replacement for silicon in future integrated circuits due to its remarkable electronic and transport properties. In order to meet technology requirements for an acceptable bandgap, graphene needs to be patterned into graphene nanoribbons (GNRs), while one-dimensional (1D) edge metal contacts (MCs) are needed to allow for the encapsulation and preservation of the transport properties. While the properties of GNRs with ideal contacts have been studied extensively, little is known about the electronic and transport properties of GNRs with 1D edge MCs, including contact resistance (RC), which is one of the key device parameters. In this work, we employ atomistic quantum transport simulations of GNRs with MCs modeled with the wide-band limit (WBL) approach to explore their metallization effects and contact resistance. By studying density of states (DOS), transmission and conductance, we find that metallization decreases transmission and conductance, and either enlarges or diminishes the transport gap depending on GNR dimensions. We calculate the intrinsic quantum limit of width-normalized RC and find that the limit depends on GNR dimensions, decreasing with width downscaling to ~3 Ω∙µm in 0.4 nm-wide GNRs, and increasing with length downscaling up to ~30 Ω∙µm in 5 nm-long GNRs. The worst-case total RC is only ~40 Ω∙µm, which demonstrates that there is room for RC improvement in comparison to the published experimental data, and that GNRs present a promising channel material for future extremely-scaled electronic nanodevices