Abstract
GaAs nanowires (NWs) are seen as promising building blocks for future optoelectronic devices. To ensure reproducible properties, a high NW uniformity is required. Here, a substantial number of both position-controlled and randomly grown self-catalyzed GaAs/AlGaAs core-shell NWs are compared. Single NWs are characterized by correlated microphotoluminescence (µ-PL) spectroscopy and transmission electron microscopy (TEM). TEM is done in the 〈110〉- and 〈112〉-projections, and on the 〈111〉-cross-section of the NWs. The position-control grown NWs showed a higher degree of uniformity in morphology. All NWs on both samples had a predominantly stacking fault free zinc blende structure, with a main optical response around the GaAs free exciton energy. However, NW-to-NW structural variations in the tip region and radial compositional variations in the shell are present in both samples. These structural features could be the origin of variations in the optical response just below and above the free exciton energy. This correlated study demonstrates that the observed distinct, sharp PL peaks in the 1.6 - 1.8 eV energy range present in several NWs, are possibly related to radial compositional variations in the AlGaAs shell rather than the structural defects in the tip region.
Published Version
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