Electronic interface and charge carrier density in epitaxial graphene on silicon carbide. A review on metal–graphene contacts and electrical gating

For over 15 years, the number of studies on graphene electronics has not ceased growing. The rich physics, a set of outstanding properties, and the envisioned range of potential applications have consolidated graphene as a research field in its own. In this Research Update, we address a specific case of graphene for electronics, epitaxial graphene on silicon carbide (SiC) substrates. This paper mainly focuses on the electronic interface of graphene with metals. The first part of this paper describes the most characteristic aspects of the growth of epitaxial graphene on SiC wafers, and the main techniques for graphene material characterization are presented first. The main objective of this paper is to gather and discuss the most representative studies on the graphene–metal interface and the strategies employed to obtain low values for the contact resistances, which is a key feature for achieving the best performance of any graphene electronic devices. To benchmark developments in specifically epitaxial graphene on SiC, we include the results on mechanically exfoliated graphene from HOPG, as well as chemical vapor deposition graphene. In the last part of this paper, relevant device architectures for electrically gating graphene are briefly discussed.