Direct correlation of crystal structure and optical properties in wurtzite/zinc-blende GaAs nanowire heterostructures

摘要

A novel method for the direct correlation at the nanoscale of structural andoptical properties of single GaAs nanowires is reported. Nanowires consistingof 100% wurtzite and nanowires presenting zinc-blende/wurtzite polytypism areinvestigated by photoluminescence spectroscopy and transmission electronmicroscopy. The photoluminescence of wurtzite GaAs is consistent with a bandgap of 1.5 eV. In the polytypic nanowires, it is shown that the regions thatare predominantly composed of either zinc-blende or wurtzite phase showphotoluminescence emission close to the bulk GaAs band gap, while regionscomposed of a nonperiodic superlattice of wurtzite and zinc-blende phasesexhibit a redshift of the photoluminescence spectra as low as 1.455 eV. Thedimensions of the quantum heterostructures are correlated with the lightemission, allowing us to determine the band alignment between these twocrystalline phases. Our first-principles electronic structure calculationswithin density functional theory, employing a hybrid-exchange functional,predict band offsets and effective masses in good agreement with experimentalresults.