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Time-resolved cathodoluminescence is a key tool with high temporal and spatial resolution. However, optical spectroscopic information can be also extracted using synchrotron pulses in a hard X-ray nanoprobe, exploiting a phenomenon called X-ray excited optical luminescence. Here, with 20 ps time resolution and 80 nm lateral resolution, we applied this time-resolved X-ray microscopy technique to individual core-shell InGaN/GaN multiple quantum well heterostructures deposited on GaN wires. Our findings suggest that the m -plane related multiple quantum well states govern the carrier dynamics. Likewise, our observations support not only the influence of In incorporation in the recombination rates, but also carrier localization phenomena at the hexagon wire apex. In addition, our experiment calls for further investigations of the spatiotemporal domain on the underlying mechanisms of optoelectronic nanodevices. Its great potential becomes more valuable when time-resolved X-ray excited optical luminescence microscopy is used in operando with other methods, such as X-ray absorption spectroscopy.

Theoretically core-multishell nanowires under a cross-section of hexagonal geometry should exhibit peculiar confinement effects. Using a hard X-ray nanobeam, here we show experimental evidence for carrier localization phenomena at the hexagon corners by combining synchrotron excited optical luminescence with simultaneous X-ray fluorescence spectroscopy. Applied to single coaxial n-GaN/InGaN multiquantum-well/p-GaN nanowires, our experiment narrows the gap between optical microscopy and high-resolution X-ray imaging and calls for further studies on the underlying mechanisms of optoelectronic nanodevices.

We present a fabrication method to produce site-controlled and regularly spaced InAs/GaAs quantum dots for applications in quantum optical information devices. The high selectivity of our epitaxial regrowth procedure can be used to allocate the quantum dots only in positions predefined by ex-situ local oxidation atomic force nanolithography. The quantum dots obtained following this fabrication process present a high optical quality which we have evaluated by microphotoluminescence and photon correlation experiments.