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In contrast to monolayer graphene, in bilayer graphene (BLG) one can induce atunable bandgap by applying an external electric field, which makes it suitablefor field effect applications. Extrinsic doping of BLGs enriches the electronicproperties of the graphene-based family, as their behavior can be switched froman intrinsic small-gap semiconductor to a degenerate semiconductor. In theframework of density functional theory (DFT) calculations, we investigate theelectronic and thermoelectric properties of BLGs doped with extrinsicimpurities from groups III (B, Al, Ga), IV (Si, Ge) and V (N, P, As), in thecontext of applied external electric fields. Doping one monolayer of the BLGwith p- or n-type dopants results in a degenerate semiconductor, where theFermi energy depends on the type of the impurity, but also on the magnitude andorientation of the electric field, which modifies the effective dopingconcentration. Doping one layer with isoelectronic species like Si and Ge opensa gap, which may be closed upon applying an electric field, in contrast to thepristine BLG. Furthermore, dual doping by III-V elements, in a way that the BLGsystem is formed by one n-type and one p-type graphene monolayer, leads tointrinsic semiconductor properties with relatively large energy gaps. Si-Si andGe-Ge substitutions render a metallic like behavior at zero field similar tothe standard BLG, however with an asymmetric density of states in the vicinityof the Fermi energy. We analyze the suitability of the highly doped BLGmaterials for thermoelectric applications, exploiting the large asymmetries ofthe density of states. In addition, a sign change in the Seebeck coefficient isobserved by tuning the electric field as a signature of narrow bands near theFermi level.

Electric and thermoelectric properties of graphene bilayers with extrinsic impurities under applied electric field