Generation-recombination processes via acoustic phonons in a disorded   graphene
  Generation-recombination interband transitions via acoustic phonons are allowed in a disordered graphene because of violation of the energy-momentum conservation requirements. The generation-recombination processes are analyzed for the case of scattering by a short-range disorder and the deformation interaction of carriers with in-plane acoustic modes. The generation-recombination rates were calculated for the cases of intrinsic and heavily-doped graphene at room temperature. The transient evolution of nonequilibrium carriers is described by the exponential fit dependent on doping conditions and disorder level. The characteristic relaxation times are estimated to be about 150 - 400 ns for sample with the maximal sheet resistance ~5 kOhm. This rate is comparable with the generation-recombination processes induced by the thermal radiation. 
F. T. Vasko and V. V. Mitin
cond-mat.mtrl-sci