Ultra-low resistance ohmic contacts in graphene field effect transistors

We report on an experimental demonstration of graphene-metal ohmic contacts with contact resistance below 100 Ω µm. These have been fabricated on graphene wafers, both with and without hydrogen intercalation, and measured using the transmission line method. Specific contact resistivities of 3 × 10⁻⁷ to 1.2 × 10⁻⁸ Ω cm² have been obtained. The ultra-low contact resistance yielded short-channel (source-drain distance of 0.45 µm) HfO₂/graphene field effect transistors (FETs) with a low on-resistance (R_on) of 550 Ω µm and a high current density of 1.7 A/mm at a source-drain voltage of 1 V. These values represent state-of-the-art (SOA) performance in graphene-metal contacts and graphene FETs. This ohmic contact resistance is comparable to that of SOA high-speed III–V high electron mobility transistors.