▎ 摘　　要

We study the instability of plasmons in a dual-grating-gate graphene field-effect transistor induced by dc current injection using self-consistent simulations with the Boltzmann equation. With only acoustic-phononlimited electron scattering, it is demonstrated that a total growth rate of the plasmon instability, with a terahertz/midinfrared range of the frequency, can exceed 4x10(12) s(-1) at room temperature, which is an order of magnitude larger than in two-dimensional electron gases based on the usual semiconductors. By comparing the simulation results with existing theory, it is revealed that the giant total growth rate originates from a simultaneous occurrence of the so-called Dyakonov-Shur and Ryzhii-Satou-Shur instabilities.