  From a combination of careful and detailed theoretical and experimental
studies, we demonstrate that the Boltzmann theory including all scattering
mechanisms gives an excellent account, with no adjustable parameters, of high
electric field transport in single as well as double-oxide graphene
transistors. We further show unambiguously that scattering from the substrate
and superstrate surface optical (SO) phonons governs the high field transport
and heat dissipation over a wide range of experimentally relevant parameters.
Models that neglect SO phonons altogether or treat them in a simple
phenomenological manner are inadequate. We outline possible strategies for
achieving higher current and complete saturation in graphene devices.
