Enhancement of surface acoustic wave amplification by drifting electrons in graphene under microwave irradiation

This paper analyzes the effect of microwave irradiation on the amplification of surface acoustic waves (SAWs) by drifting electrons in graphene. An expression is obtained for the SAW gain G as a function of the frequency and intensity of microwaves, the electron drift velocity, and the parameters of the considered graphene/piezoelectric substrate hybrid structure. Our calculations show that in the presence of microwave radiation incident normally on the graphene layer and polarized along the direction of SAW propagation, the SAW gain G, measured in units of dB/cm, can be several times greater than in the presence of only an applied dc electric field causing electron drift. The results obtained indicate an effective way to improve the performance of ultra-compact graphene-based SAW amplifiers.