Electronic structure of InAs/GaSb core-shell nanowires

The electronic and optical properties of InAs/GaSb core-shell nanowires are investigated within the effective mass k·p approach. These systems have a broken band gap, which results in spatially separated confinement of electrons and holes. We investigated these structures for different sizes of the InAs and GaSb core and shell radius. We found that for certain configurations, the conduction band states penetrate into the valence band states resulting in a negative band gap (Eg<0), which leads to a conduction band ground state that lies below the valence band ground state at the Γ point. For certain core-shell wires, only one conduction band state penetrates into the valence band and in this case, a minigap Δ opens up away from the Γ point and as a consequence the electronic properties of the nanowire now depend on both Eg and Δ values.