Quantum mechanical analysis of a THz graphene travelling wave amplifier

In this paper, the possibility of travelling wave amplification in graphene at the THz range of frequency is explored using a quantum mechanical model. Graphene as a zero overlap semi-metal can be easily doped electrically. Due to high mobility of electrons and holes in graphene, high drift velocities can be induced by applying a DC voltage across the graphene sheet. In this paper, the interaction between the EM wave and carriers in graphene is analysed. The linear response theory is applied to find the induced current and conductivity in the presence of an incident electromagnetic wave. The results show that the negative conductivity and in turn electromagnetic amplification in microwave and THz frequencies can be obtained for drift velocities slightly greater than the phase velocity at room temperature. With this property, graphene can be used in future solid state travelling wave amplifiers instead of its semiconductor counterparts.