Determination of GaAs zinc blende/wurtzite band offsets utilizing GaAs nanowires with an axial GaAsSb insert

By applying a correlated micro-photoluminescence spectroscopy and transmission electron microscopy (TEM) approach, we have utilized molecular beam epitaxy grown self-catalysed GaAs nanowires (NWs) with an axial GaAsSb insert to determine the band offsets at the crystal phase heterojunction between zinc blende (ZB) and wurtzite (WZ) GaAs. Two distinct PL emission bands originating from the ZB GaAsSb insert were identified. The lower energy PL emission allowed an independent verification of the maximum Sb molar fraction to be ∼30%, in agreement with quantitative high-angle annular dark field scanning TEM performed on the same single NW. The higher energy PL emission revealed a low temperature ZB/WZ band offset of 120 meV at the interface between the two GaAs crystal phases occurring at the upper boundary of the insert. Separate conduction and valence band offsets develop at a higher temperature due to the different temperature dependence of the ZB and WZ GaAs band gaps, but both offset values show a relatively little variation in the range of 10–150 K