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Autoren: Tomadin, Andrea
Hornett, Sam M.
Wang, Hai I.
Alexeev, Evgeny M.
Candini, Andrea
Coletti, Camilla
Turchinovich, Dmitry
Kläui, Mathias
Bonn, Mischa
Koppens, Frank H. L.
Hendry, Euan
Polini, Marco
Tielrooij, Klaas-Jan
Titel: The ultrafast dynamics and conductivity of photoexcited graphene at different Fermi energies
Online-Publikationsdatum: 26-Aug-2019
Erscheinungsdatum: 2018
Sprache des Dokuments: Englisch
Zusammenfassung/Abstract: For many of the envisioned optoelectronic applications of graphene, it is crucial to understand the subpicosecond carrier dynamics immediately following photoexcitation and the effect of photoexcitation on the electrical conductivity—the photoconductivity. Whereas these topics have been studied using various ultrafast experiments and theoretical approaches, controversial and incomplete explanations concerning the sign of the photoconductivity, the occurrence and significance of the creation of additional electron-hole pairs, and, in particular, how the relevant processes depend on Fermi energy have been put forward. We present a unified and intuitive physical picture of the ultrafast carrier dynamics and the photoconductivity, combining optical pump–terahertz probe measurements on a gate-tunable graphene device, with numerical calculations using the Boltzmann equation. We distinguish two types of ultrafast photo-induced carrier heating processes: At low (equilibrium) Fermi energy (EF ≲ 0.1 eV for our experiments), broadening of the carrier distribution involves interband transitions (interband heating). At higher Fermi energy (EF ≳ 0.15 eV), broadening of the carrier distribution involves intraband transitions (intraband heating). Under certain conditions, additional electron-hole pairs can be created [carrier multiplication (CM)] for low EF, and hot carriers (hot-CM) for higher EF. The resultant photoconductivity is positive (negative) for low (high) EF, which in our physical picture, is explained using solely electronic effects: It follows from the effect of the heated carrier distributions on the screening of impurities, consistent with the DC conductivity being mostly due to impurity scattering. The importance of these insights is highlighted by a discussion of the implications for graphene photodetector applications.
DDC-Sachgruppe: 530 Physik
530 Physics
Veröffentlichende Institution: Johannes Gutenberg-Universität Mainz
Organisationseinheit: FB 08 Physik, Mathematik u. Informatik
Veröffentlichungsort: Mainz
ROR: https://ror.org/023b0x485
DOI: http://doi.org/10.25358/openscience-112
URN: urn:nbn:de:hebis:77-publ-592173
Version: Accepted version
Publikationstyp: Zeitschriftenaufsatz
Nutzungsrechte: Urheberrechtsschutz
Informationen zu den Nutzungsrechten: https://rightsstatements.org/vocab/InC/1.0/
Zeitschrift: Science advances
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Seitenzahl oder Artikelnummer: eaar5313
Verlag: Assoc.
Verlagsort: Washington, DC u.a.
Erscheinungsdatum: 2018
ISSN: 2375-2548
URL der Originalveröffentlichung: http://dx.doi.org/10.1126/sciadv.aar5313
DOI der Originalveröffentlichung: 10.1126/sciadv.aar5313
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