Ultrafast carrier dynamics in Ge by ultra-broadband mid-infrared probe spectroscopy.

ABSTRACT: In this study, we carried out 800-nm pump and ultra-broadband mid-infrared (MIR) probe spectroscopy with high time-resolution (70?fs) in bulk Ge. By fitting the time-resolved difference reflection spectra [?R(?)/R(?)] with the Drude model in the 200-5000?cm^-1 region, the time-dependent plasma frequency and scattering rate have been obtained. Through the calculation, we can further get the time-dependent photoexcited carrier concentration and carrier mobility. The Auger recombination essentially dominates the fast relaxation of photoexcited carriers within 100?ps followed by slow relaxation due to diffusion. Additionally, a novel oscillation feature is clearly found in time-resolved difference reflection spectra around 2000?cm^-1 especially for high pump fluence, which is the Lorentz oscillation lasting for about 20?ps due to the Coulomb force exerted just after the excitation.

SUBMITTER: Yeh TT 

PROVIDER: S-EPMC5225453 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature