Bottom-gated epitaxial graphene

High-quality epitaxial graphene on silicon carbide (SiC) is today available in wafer size(1,2). Similar to exfoliated graphene(3,4), its charge carriers are governed by the Dirac-Weyl Hamiltonian5-7 and it shows excellent mobilities(7,8). For many experiments with graphene, in particular for surface science, a bottom gate is desirable(9-13). Commonly, exfoliated graphene flakes are placed on an oxidized silicon wafer that readily provides a bottom gate(3,4,11). However, this cannot be applied to epitaxial graphene as the SiC provides the source material out of which graphene grows. Here, we present a reliable scheme for the fabrication of bottom-gated epitaxial graphene devices, which is based on nitrogen (N) implantation into a SiC wafer and subsequent graphene growth. We demonstrate working devices in a broad temperature range from 6 to 300 K. Two gating regimes can be addressed, which opens a wide engineering space for tailored devices by controlling the doping of the gate structure.