Valley featured electronic transport of pn junction in silicene ribbon

• Parameter dependence of the conductance of silicene pn junctions with spin–orbit coupling.
• Effect of energy gap and edge states on the pn-tunneling conductance.
• Explanation for all transport features by means of a simple subband-tunneling model.

We calculated the conductance of silicene pn junction in the bipolar region using the non-equilibrium retarded Green's function method. When an electrical field is applied normally, the energy gaps of valleys K   and K′K′ become different. The conductance of pn junctions is mainly determined by the transport of electrons of the valley with the smaller gap, and the conductance of the other valley can also be observed for short junctions. For the spin–orbit coupling dominant cases, edge state bands lie in the bulk gap and contribute a unit tunneling conductance plateau, which is independent of the junction length. When changing electrical field continuously, the conductance peaks at a certain position for long junctions but decreases monotonically for short junctions. We explained all these features based on a simple subband tunneling model.