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

Tien Tien Yeh, Hideto Shirai, Chien Ming Tu, Takao Fuji, Takayoshi Kobayashi, Chih Wei Luo*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

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 [δR(ω)/R(ω)] 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.

Original languageEnglish
Article number40492
JournalScientific reports
Volume7
DOIs
StatePublished - 11 Jan 2017

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