  Ballistic quantum transport calculations based on the non-equilbrium Green's
function formalism show that field-effect transistor devices made from
chevron-type graphene nanoribbons (CGNRs) could exhibit negative differential
resistance with peak-to-valley ratios in excess of 4800 at room temperature as
well as steep-slope switching with 6 mV/decade subtheshold swing over five
orders of magnitude and ON-currents of 88$\mu$A/$\mu$m. This is enabled by the
superlattice-like structure of these ribbons that have large periodic unit
cells with regions of different effective bandgap, resulting in minibands and
gaps in the density of states above the conduction band edge. The CGNR ribbon
used in our proposed device has been previously fabricated with bottom-up
chemical synthesis techniques and could be incorporated into an
experimentally-realizable structure.
