Theory of nonlinear microwave absorption in an electron-doped and gapped graphene monolayer

Abstract

Abstract We present a theory of nonlinear microwave absorption in monolayer graphene grown epitaxially on a SiC substrate and electron-doped by electrostatic gating. The intensity-dependent absorption coefficient of normally incident microwave radiation is calculated by using the Boltzmann equation techniques. The Boltzmann transport equation for mobile carriers in the conduction band of the graphene layer is solved to third order in the applied microwave field, including nonlinearities due to both the nonparabolicity of the conduction band and the energy-dependent scattering rate of electrons by acoustic phonons and short-range lattice defects. The intraband absorption coefficient decreases with an increase in the intensity of incident radiation, thus suggesting that electron-doped epitaxial graphene may be exploited as a saturable absorber operating at microwave frequencies. The saturation intensity is calculated as a function of excitation frequency and electron concentration and found to be a few MW/cm 2 over the millimeter wave frequency band considered (30–300 GHz) at a typical doping level of 1012 cm−2.