Microwave parameters dependence on Graphene Field Effect Transistors (GFETs) dimensions

Graphene is a relatively new material whose unique properties have attracted significant interest for its use in electronic and photonic applications. In particular, field effect has been proved in graphene samples and this feature, together with the high carrier mobility observed, makes graphene an interesting solution for high frequency electronics. In our work, we performed a statistical analysis in order to evaluate the microwave parameters dependence on Graphene Field Effect Transistors (GFETs) dimensions. In more detail, for the first time, we studied the behavior of the cut-off frequency (ft) and of the output impedance (Zout) at varying both the gate-drain/gate-source distance (Δ) and the gate length (Lg). In order to perform the abovementioned statistical analysis, we fabricated 24 GFETs families on the same chip. Each family is composed of 10 equal devices, with the same Δ and Lg values. After their fabrication, the GFETs were characterized in both DC and RF regimes. DC measurements allowed us to obtain the transconductance curves (Id vs Vgs) and, hence, to evaluate the static transconductance (gm), whose value deeply influences the cut-off frequency. The scattering parameters were then measured, in the region where gm shows its highest value, by using a vector network analyzer. This allowed us to evaluate the short circuit current gain (h21), ft and Zout.