Title: Ultrafast carrier dynamics in Ge by ultra-broadband mid-infrared probe spectroscopy
Authors: Yeh, Tien-Tien
Shirai, Hideto
Tu, Chien-Ming
Fuji, Takao
Kobayashi, Takayoshi
Luo, Chih-Wei
Department of Electrophysics
Issue Date: 11-Jan-2017
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 [Delta R(omega)/R(omega)] 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.
URI: http://dx.doi.org/10.1038/srep40492
ISSN: 2045-2322
DOI: 10.1038/srep40492
Volume: 7
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