Optical absorption modulation by selective codoping of SiGe core-shell nanowires

First-principles calculations on the structural, electronic, and optical properties of B-P codoped SiGe core-shell nanowires are discussed. We show that the simultaneous addition of B and P impurities into the wire can be energetically favored with respect to the single-doping. We demonstrate that impurities energetic levels in the band gap are dependent by the Si/Ge band offset, as well as by their location in the wire (i.e., core or shell region). This electronic tunability results in a significant optical modulation, as demonstrated by the red-shift of the first optical peak when B and P locations are switched in the wire