Negative differential resistance in new structures based on graphene nanoribbons

Six new structures based on graphene nanoribbons are proposed, all of which show negative differential resistance (NDR) in their I-V characteristics. Electron transfer in these structures is based on intraband tunneling, interband resonant tunneling, or simple interband tunneling. The I-V characteristics of the structures are investigated using a -orbital tight-binding approach and the nonequilibrium Green's function formalism. Atomically precise doping with boron and/or nitrogen impurities as well as careful selection of nanoribbon width have been used to achieve desired energy-band structures. The introduced structures are found to offer good flexibility to fulfill circuit requirements in terms of peak/valley voltages and currents as well as high speed. In these new structures, the peak current ranges from 5.5 to 1300 nA, the peak voltage from 24 to 115 mV, the peak-valley ratio at room temperature from 34 to 8582, and the NDR width from 40 to 180 mV. Effects of different temperatures are also explored, and the results reported.