  A theory is developed for interband tunneling in semiconducting carbon
nanotube and graphene nanoribbon p-n junction diodes. Characteristic length and
energy scales that dictate the tunneling probabilities and currents are
evaluated. By comparing the Zener tunneling processes in these structures to
traditional group IV and III-V semiconductors, it is proved that for identical
bandgaps, carbon based 1D structures have higher tunneling probabilities. The
high tunneling current magnitudes for 1D carbon structures suggest the distinct
feasibility of high-performance tunneling-based field-effect transistors.
