**4. Graphene Field Effect Transistors (GFETs) and Radio Frequency (RF) electronics**

There has been an interest in looking at graphene for nanoelectronics applications due to its high intrinsic mobility allowing for greater switching speed. [18] The main problem with the integration of graphene into three-terminal devices is the lack of a high Ion/Ioff current, which for regular metal oxide semiconductor field effect transistors (MOSFETs) is on the order of 104 –107 , while for most graphene devices is on the order of 10. [16, 55] This makes graphenebased devices more attractive for the replacement of RF-based devices that are currently dominated by high electron mobility transistors (HEMT) that require a Ion/Ioff ratio of around 30. [16, 55] In addition to this, RF electronics require current saturation to obtain voltage and power gains of around 30, which for graphene means the creation of a band gap through one of the doping mechanisms described above. [16] Saturation current is normally attained through the saturation of charge carrier velocity; however, due to the high mobility of the graphene layer the velocity saturation is unattainable without going to extremely high source drain voltage. [16] Therefore, saturation must be obtained through current pinchoff effects and voltage gain as shown in Figure 17, which can be created in graphene through band gap formation. [16] Even with the formation of a band gap, graphene does not exhibit a saturation current at zero doping due to the Fermi-Dirac cone shape, but the band gap does allow the creation of current pinchoff due to electrical band gap modulation via the source and drain contacts. With this background, we are going to address in the subsequent section several issues that hinder the integration of graphene into FETs that can be utilized for RF applications and review the state-of-the-art technology in terms of GFETs for RF electronics.

**Figure 17.** Diagram showing current pinchoff in a Si MOSFET.
