Ultrafast optical-pump terahertz-probe spectroscopy of the carrier relaxation and recombination dynamics in epitaxial graphene.

George, Paul A; Strait, Jared; Dawlaty, Jahan; Shivaraman, Shriram; Chandrashekhar, Mvs; Rana, Farhan; Spencer, Michael G · Nano Lett · 2008

basic_science · Level V

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Abstract

The ultrafast relaxation and recombination dynamics of photogenerated electrons and holes in epitaxial graphene are studied using optical-pump terahertz-probe spectroscopy. The conductivity in graphene at terahertz frequencies depends on the carrier concentration as well as the carrier distribution in energy. Time-resolved studies of the conductivity can therefore be used to probe the dynamics associated with carrier intraband relaxation and interband recombination. We report the electron-hole recombination times in epitaxial graphene for the first time. Our results show that carrier cooling occurs on subpicosecond time scales and that interband recombination times are carrier density dependent.