Ultrafast nano-imaging of many-body carrier dynamics in semiconductor nanowires

The study of carrier dynamics in semiconductor nanostructures serves as testbed for understanding many-body interactions and is foundational for advancing nanoscale optoelectronics.

However, diffraction-limited far-field spectroscopies obscure not only the role of nanocale spatial heterogeneities but also the relative contributions of surface versus bulk recombination. Here, we employ ultrafast heterodyne visible pump–mIR probe nanoimaging of individual MBE-grown InAs nanowires to map carrier relaxation in space and time. We observe a pump-fluence dependent relaxation, with faster surface recombination at small tip tapping amplitudes and longer-lived bulk responses at larger amplitudes. Further, combining ultrafast nano-imaging with far-field dynamics allows to disentangle the surface-localized dynamics from bulk effects. Using a Drude model we describe the aggregate of spatial-, fluence-, and frequency-dependent results self-consistently with a excitation density dependent recombination rate. The convergence between near-field and far-field pump-probe results puts near-field pump–probe nanoimaging on a quantitative foundation as a tool for resolving carrier dynamics in nanoscale semiconductors as basis for their targeted parameter optimization for device applications.