Doped Graphene on Silicon Bottom Gated FET for High Drain Current and Applications in RF And Logic Circuits

Single Si-substituted monolayer Si-doped graphene (Si:Gr) with one carbon atom in hexagon of graphene substituted by Si atom, studied by density functional theory (DFT) calculation has a range of structural and electronic features. The Si:Gr demonstrates absorbed-atom geometric structure, silicon-carbon dominated energy bands, atom-orbital projected density of states and charge concentration in space. These critical characteristics generate distinct physical and electrical properties of the unique material Si:Gr permitting it to be utilized as semiconductor material. Due to very high carrier mobility and saturation velocity, graphene devices are very useful in radio frequency (RF) applications. Recent studies suggest that utilizing bare silicon as a supporting substrate without an insulating layer under the channel region in conventional graphene-field effect transistor (GFET) can result in high output resistance and voltage gain, which provides higher cut-off frequency comparing with conventional GFET. In this work, an N-channel GFET with printed channel length of 50nm has been designed with Si:Gr as channel material where the Si:Gr is deposited on lightly doped p-type silicon substrate eliminating the insulator layer in between. For optimum RF performance bottom gate with SiO
2
as back gate dielectric has been utilized. The device has provided a maximum cut-off frequency of 788GHz and Ion/Ioff ratio of
$4.7\times 10^{6}$
(bottom gate, metallic contact) proposing a novel device for RF and logic circuit applications.