We have studied the response of the graphene with a gap to external dc and ac electric fields without using of low-energy approximation for the energy carrier that allows us to study the effects of a broader range of parameters of applied electric fields. The electronic system of graphene described by Boltzmann's kinetic equation in the constant relaxation-time approximation. The amplitude of the higher harmonics on the characteristics of applied fields is studied.
Faculty of Mathematics, Computer Science and Physics, Volgograd State Social Pedagogical University. Volgograd, 400001 Russia.