The electronic transport in few-layer black phosphorus (FLBP) nanoribbons is studied theoretically. The system is modeled on the basis of band structures, which have been measured recently by $\mu$-ARPES experiments. We show that the anisotropic bands of FLBP lead to highly anisotropic transport properties; while the current in one direction can be rather focused, it can be strongly dispersed in the orthogonal direction. The low-energy current is concentrated in the central layers due to the vertical confinement of the electrons. In FLBP pn junctions, generated by the electrostatic potential of a gate contact, the electrons pass through the interface of the junction, if it is oriented along the zigzag direction of FLBP. If the junction is rotated by 90 degrees and oriented along the armchair direction, the current is reflected completely for all angles of incidence and for a wide range of electron energies. This omnidirectional total reflection is named anti-super-Klein tunneling because of opposite pseudospins of the electrons in the two regions of the pn junction. The effect is quite independent from the number of layers and should be observed even in the bulk. The effect of oxidation of the top layer of FLBP pn junctions is investigated and it is found that, while the current flow in the top layers is strongly suppressed, the anti-super-Klein tunneling persists.

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• Quantum transport
• Layered crystals
• Phosphorene
• Green's function methods
• Tight-binding model