Study of core/shell GaAs/AlAs heterostructure nanowires

Achieving significant doping in GaAs/AlAs core/shell nanowires (NWs) is of considerable technological importance but is challenging due to the amphoteric behavior of the dopant atoms. We studied a GaAs/AlAs core/shell heterostructure with a narrow GaAs quantum well embedded in the AlAs shell effectively getters residual carbon atoms leading to unintentional p-type doping. Magneto-optical studies of such GaAs/AlAs core multi-shell NW reveal quantum confined emission, which is observed above the energy corresponding to the band gap of bulk GaAs.  Such emission is absent in the optical spectra of single GaAs/AlAs core shell nanowires with comparable diameter. Theoretical calculations of NW electronic structure confirm quantum confinement of carriers at the core/shell interface due to the presence of ionized carbon acceptors in the 1 nm GaAs layer in the shell. Micro-photoluminescence in high magnetic field shows a clear signature of avoided crossings of the n = 0 Landau level emission line with the n = 2 Landau level TO phonon replica. The coupling is caused by the resonant hole-phonon interaction, which is a fingerprint of the large 2D hole density in the nanowire heterostructure.