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Title: Carrier heating and negative photoconductivity in graphene

We investigated negative photoconductivity in graphene using ultrafast terahertz techniques. Infrared transmission was used to determine the Fermi energy, carrier density, and mobility of p-type chemical vapor deposition graphene samples. Time-resolved terahertz photoconductivity measurements using a tunable mid-infrared pump probed these samples at photon energies between 0.35‚ÄČeV and 1.55‚ÄČeV, approximately one-half to three times the Fermi energy of the samples. Although interband optical transitions in graphene are blocked for pump photon energies less than twice the Fermi energy, we observe negative photoconductivity at all pump photon energies investigated, indicating that interband excitation is not required to observe this effect. Our results are consistent with a thermalized free-carrier population that cools by electron-phonon scattering, but are inconsistent with models of negative photoconductivity based on population inversion.
Authors:
; ; ;  [1] ;  [2] ;  [3]
  1. Macalester College, St. Paul, Minnesota 55105 (United States)
  2. School of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455 (United States)
  3. Naval Research Laboratory, Washington, District of Columbia 20375 (United States)
Publication Date:
OSTI Identifier:
22399227
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 1; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; APPROXIMATIONS; CARRIER DENSITY; CARRIER MOBILITY; CHEMICAL VAPOR DEPOSITION; ELECTRON-PHONON COUPLING; ELECTRONS; EV RANGE; EXCITATION; GRAPHENE; HEATING; PHONONS; PHOTOCONDUCTIVITY; PHOTONS; POPULATION INVERSION; P-TYPE CONDUCTORS; SCATTERING; TIME RESOLUTION