Current Driven Plasma Instability in Graphene-FETs with Coulomb Electron Drag

We show that the ballistic electron injection from the n+ source region through the i-region into the gated n-region of the n+-i-n-n+ graphene field-effect transistor (GFET) leads to the effective drag of quasi-equilibrium electrons toward the drain. The drag results in the positive feedback between the ballistic injection and the reverse injection from the n+ drain region and can lead to the negative real part of the GFET source-drain impedance accompanied with the change of the impedance imaginary part sign. As a result, the steady-state current flow along the GFET channel can be unstable giving rise to the current driven self-excitation of the electron density high-frequency oscillations (plasma instability). The related oscillations of the current feeding an antenna can be used for the terahertz radiation emission.