Knut Müller-Caspary, Tim Grieb, Jan Müßener, Nicolas Gauquelin, Pascal Hille, Jörg Schörmann, Johan Verbeeck, Sandra Van Aert, Martin Eickhoff, Andreas Rosenauer

Physical Review Letters (2019) 122, 106102

https://doi.org/10.1103/PhysRevLett.122.106102

We report the mapping of polarization-induced internal electric fields in AlN/GaN nanowire heterostructures at unit cell resolution as a key for the correlation of optical and structural phenomena in semiconductor optoelectronics. Momentum-resolved aberration-corrected scanning transmission electron microscopy is employed as a new imaging mode that simultaneously provides four-dimensional data in real and reciprocal space. We demonstrate how internal mesoscale and atomic electric fields can be separated in an experiment, which is verified by comprehensive dynamical simulations of multiple electron scattering. A mean difference of 5.3±1.5  MV/cm is found for the polarization-induced electric fields in AlN and GaN, being in accordance with dedicated simulations and photoluminescence measurements in previous publications.