A selection rule for interband tunneling in nanowires with a tight-binding NEGF formalism

Interband tunneling in nanowires was studied with a non-equilibrium Green's function (NEGF) method focusing on the incident and outgoing eigenstates of the left and right leads. Tunneling is allowed only between paired lead eigenstates linked to each other via an imaginary wavevector in the forbidden gap. Following Kane's tunneling theory, we believe that the tunneling for typical semiconductor materials is associated with the coupling between the s and p atomic orbitals, similar to the selection rule for optical transitions. The tunneling efficiencies for both homojunctions and heterojunctions are compared to select optimal materials.