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In the framework of the European project Flagship Graphene, we have developed several process technologies, for fabricating graphene field-effect transistors, for radio frequency (RF) applications. Depending on the technique used to synthesize graphene, different transistors topologies were designed, given rise to different applications. Graphene materials under consideration include graphene growth on silicon carbide, graphene growth by chemical vapor deposition (CVD) on copper foil. After fabrication of transistors on rigid and on flexible substrates, high frequency characterization of devices is made. Based on the performance of transistors, RF circuits where designed and fabricated.

In this letter we present our work on top-gated graphene field-effect transistors GFET. The Transistors have been processed on epitaxial graphene synthesized on the Si-face of a SiC substrate, using a high-k dielectric Al 2 O 3 as a gate oxide. In order to reduce the gate access resistance, we chosed a T-gate geometry. The Hall mobility is on the order 780 cm2/vs at room temperature, for an intrinsic carrier concentration of the order of 8.7 10+12 /cm2. We used Nickel as a contact material, The contact resistance was measured by the Transmission Line Method (TLM) where the value of ρ c is 2 × 10−6 Ω.cm2. We characterized our devices from DC up to 67 GHz. Cut-off frequency f t as high as 90 GHz has been obtained for the 170 nm gate length transistors. The maximum value of f t is 43 GHz and the maximum value of f max is 23 GHz. Finally, we studied the homogeneity of the GFETS realized across the whole sample surface (1/4 of inch).

International audience; This paper deals with both DC and high frequency characterization of graphene devices, associated to compact electrical modelling. Pulsed I-V and microwave characterization of several Graphene Field-Effect Transistor (GFET) generations fabricated on SiC substrates were investigated in order to derive a first approach for non-linear device modelling. As illustrated here with a Graphene Nano Ribbon FET (GNR FET), a compact electrical model was presented accounting the DC and HF characteristics in broad range of operating conditions. The differences between DC and pulsed I-V characterizations of the GNR FET are investigated and compared to simulations. The small signal behavior and some figure of merits (FOM) like current gain cut-off frequency ft maximum oscillation frequency fmax. The nonlinear modelling of GNR FET is becoming of prime importance along with technological efforts to demonstrate the actual potential of this promising technology. This approach was also applied to conventional GFET, with a large flake of graphene used as a device channel.