The characteristics of tunnel junctions formed between n- and p-doped
graphene are investigated theoretically. The single-particle tunnel current
that flows between the two-dimensional electronic states of the graphene (2D-2D
tunneling) is evaluated. At a voltage bias such that the Dirac points of the
two electrodes are aligned, a large resonant current peak is produced. The
magnitude and width of this peak is computed, and its use for devices is
discussed. The influence of both rotational alignment of the graphene
electrodes and structural perfection of the graphene is discussed.Comment: 23 pages, 9 figures; added Section II(E) and associated figures, and
made other minor typographical correction