Nanoscale mapping of carrier recombination in GaAs/AlCaAs core-multishell nanowires by cathodoluminescence imaging in a scanning transmission electron microscope

摘要

Mapping individual radiative recombination channels at the nanoscale in direct correlation with the underlying crystal structure and composition of III-V semiconductor nanostructures requires unprecedented highly spatially resolved spectroscopy methods. Here, we report on a direct one-by-one correlation between the complex radial structure and the distinct carrier recombination channels of single GaAs-AlGaAs core-multishell nanowire heterostructures using low temperature cathodoluminescence spectroscopy directly performed in a scanning transmission electron microscope. Based on an optimized focused ion beam fabrication of the optically active specimen, we directly visualize the radial luminescence evolution and identify four distinct emission lines, i.e., the near band edge and defect luminescence of the GaAs core (819 nm, 837 nm), the emission of the single embedded GaAs quantum well (QW, 785 nm), and the AlGaAs shell luminescence correlated with alloy fluctuations (650-674 nm). The detailed radial luminescence profiles are anticorrelated between QW luminescence and core emission, illustrating the radial carrier transport of the core-shell system. We inspected in detail the low-temperature capture of excess carriers in the quantum well and barriers.