Electron-hole generation and recombination rates for Coulomb scattering in graphene

We calculate electron-hole generation and recombination rates for Coulomb scattering (Auger recombination and impact ionization) in zero band-gap graphene. The conduction and valence band dispersion relation in graphene together with energy and momentum conservation requirements restrict the phase space for Coulomb scattering so that electron-hole recombination times can be much longer than 1 ps for electron-hole densities smaller than 10(12) cm(-2).