Photoexcited carrier and phonon morphology of InSb observed with an ultrafast pump-probe microscope

Abstract

The ultrafast pump-probe microscope has been utilized to spatially map the ultrafast dynamics of photoexcited carriers and phonons in InSb with varied carrier concentrations. In this study, the negative and positive components of transient reflectivity-change spectra (ΔR/R) are associated with the dynamics of photoexcited holes and phonons, respectively. The mapping of phonon morphology (i.e. positive ΔR/R on a ps-ns timescale) shows the delocalized electron-phonon coupling in InSb, especially for large carrier concentrations. In contrast, the recombination of electrons and holes is rather localized inside the pumped spot. According to morphological analyses of oscillatory signals in ΔR/R, we found that an electric field applied to InSb can further manipulate the phonon strength and lifetime. For the case of large carrier concentrations, the spatial breadth of phonons has been first observed in InSb.