▎ 摘　　要

The heating of carriers in an intrinsic graphene under abrupt switching on of a dc electric field is examined, taking into account both the energy relaxation via acoustic and optic phonons and the interband generation-recombination processes. The latter are caused by the interband transitions due to optical phonon modes and thermal radiation. A description of the temporal and steady-state responses, including the nonequilibrium concentration and energy as well as the current-voltage characteristics, is given. At room temperature, a nearly linear current-voltage characteristic and a slowly varied concentration occur for fields up to similar to 20 kV/cm. Because of a predominant recombination of high-energy carriers due to optical phonon emission at low temperatures, a depletion of concentration takes place below similar to 250 K. For lower temperatures the current tends to be saturated and a negative differential conductivity appears below similar to 170 K in the region of fields similar to 10 V/cm.