Photoconductivity

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A J Heeger - One of the best experts on this subject based on the ideXlab platform.

Qing Chen - One of the best experts on this subject based on the ideXlab platform.

  • switching from negative to positive Photoconductivity toward intrinsic photoelectric response in inas nanowire
    ACS Applied Materials & Interfaces, 2017
    Co-Authors: Yuxiang Han, Zhiqiang Tang, Xiao Zheng, Xiaoye Wang, Weijian Lin, Tao Yang, Qing Chen
    Abstract:

    Negative Photoconductivity (NPC) and positive Photoconductivity (PPC) are observed in the same individual InAs nanowires grown by metal–organic chemical vapor deposition. NPC displays under weak light illumination due to photoexcitation scattering centers charged with hot carrier in the native oxide layer. PPC is observed under high light intensity. Through removing the native oxide layer and passivating the nanowire with HfO2, we eliminate the NPC effect and realize intrinsic photoelectric response in InAs nanowire.

  • negative Photoconductivity of inas nanowires
    Physical Chemistry Chemical Physics, 2016
    Co-Authors: Yuxiang Han, Xiao Zheng, Dong Pan, Yao Guo, Jianhua Zhao, Qing Chen
    Abstract:

    Negative Photoconductivity is observed in InAs nanowires (NWs) without a surface defective layer. The negative Photoconductivity is strongly dependent on the wavelength and intensity of the light, and is also sensitive to the environmental atmosphere. Two kinds of mechanisms are discerned to work together. One is related to gas adsorption, which is photodesorption of water molecules and photo-assisted chemisorption of O2 molecules. The other one can be attributed to the photogating effect introduced by the native oxide layer outside the NWs.

J N Heyman - One of the best experts on this subject based on the ideXlab platform.

  • thz transient Photoconductivity of the iii v dilute nitride gap y as1 y x n x
    Semiconductor Science and Technology, 2018
    Co-Authors: J N Heyman, E M Weiss, J R Rollag, O D Dubon, Y J Kuang, W Walukiewicz
    Abstract:

    Author(s): Heyman, JN; Weiss, EM; Rollag, JR; Yu, KM; Dubon, OD; Kuang, YJ; Tu, CW; Walukiewicz, W | Abstract: © 2018 IOP Publishing Ltd. THz Time-Resolved Photoconductivity is used to probe carrier dynamics in the dilute III-V nitride GaP0.49As0.47N0.036. In these measurements a femtosecond optical pump-pulse excites electron-hole pairs, and a delayed THz pulse measures the change in conductivity. We find the Photoconductivity is dominated by localized carriers. The decay of Photoconductivity after excitation is consistent with bimolecular electron-hole recombination with recombination constant r = 3.2 0.8 10-8 cm3 s-1. We discuss the implications for applications in solar energy.

  • thz transient Photoconductivity of the iii v dilute nitride gapasn
    arXiv: Materials Science, 2018
    Co-Authors: J N Heyman, E M Weiss, J R Rollag, O D Dubon, Y J Kuang, W Walukiewicz
    Abstract:

    THz Time-Resolved Photoconductivity is used to probe carrier dynamics in the dilute III-V nitride GaP0.49As0.47N0.036. In these measurements a femtosecond optical pump-pulse excites electron-hole pairs, and a delayed THz pulse measures the change in conductivity. We find the Photoconductivity is dominated by localized carriers. The decay of Photoconductivity after excitation is consistent with bimolecular electron-hole recombination with recombination constant r = 3.2E-8 +/-0.8E-8 cm3/s. We discuss the implications for applications in solar energy.

  • THz transient Photoconductivity of the III-V dilute nitride GaP y As1-y-xN x
    eScholarship University of California, 2018
    Co-Authors: J N Heyman, E M Weiss, O D Dubon, Y J Kuang, Walukiewicz W.
    Abstract:

    THz Time-Resolved Photoconductivity is used to probe carrier dynamics in the dilute III-V nitride GaP As N . In these measurements a femtosecond optical pump-pulse excites electron-hole pairs, and a delayed THz pulse measures the change in conductivity. We find the Photoconductivity is dominated by localized carriers. The decay of Photoconductivity after excitation is consistent with bimolecular electron-hole recombination with recombination constant r = 3.2 0.8 10 cm s . We discuss the implications for applications in solar energy. 0.49 0.47 0.036 -8 3 -

  • carrier heating and negative Photoconductivity in graphene
    Journal of Applied Physics, 2015
    Co-Authors: J N Heyman, J D Stein, Z S Kaminski, A R Banman, Aaron M Massari, Jeremy T Robinson
    Abstract:

    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 eV and 1.55 eV, 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.

  • carrier heating and negative Photoconductivity in graphene
    arXiv: Materials Science, 2014
    Co-Authors: J N Heyman, J D Stein, Z S Kaminski, A R Banman, Aaron M Massari, Jeremy T Robinson
    Abstract:

    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 CVD graphene samples. Time-resolved terahertz Photoconductivity measurements using a tunable mid-infrared pump probed these samples at photon energies between 0.35eV to 1.55eV, 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 inconsistent with models of negative Photoconductivity based on population inversion.

Balaji Panchapakesan - One of the best experts on this subject based on the ideXlab platform.

  • Photoconductivity in single wall carbon nanotube sheets
    Nanotechnology, 2006
    Co-Authors: Balaji Panchapakesan
    Abstract:

    In this paper we report for the first time, the Photoconductivity of large area sheets of single wall carbon nanotube upon laser illumination. The Photoconductivity exhibited an increase, decrease or even 'negative' values when the laser spot was on different positions between contact electrodes, showing a 'position' dependent effect of Photoconductivity. Photon induced charge carrier generation in single wall carbon nanotubes and subsequent charge separation across the metal?carbon nanotube contacts is believed to cause the Photoconductivity changes. A net photovoltage of ~10?mV and a photocurrent of ~1.6?mA were produced under the laser intensity of ~160?mW with a quantum efficiency of ~1.5% in vacuum. The effect of the contact area between the electrodes and nanotubes, ambient pressure, laser intensity and light pulse frequency on the Photoconductivity is discussed.

Fred Wudl - One of the best experts on this subject based on the ideXlab platform.

  • sensitization of the Photoconductivity of conducting polymers by c60 photoinduced electron transfer
    Physical Review B, 1993
    Co-Authors: Gang Yu, D Moses, N S Sariciftci, A J Heeger, K Pakbaz, C Zhang, Fred Wudl
    Abstract:

    We have investigated the effect of photoinduced electron transfer on the Photoconductivity (PC) of conducting polymer-C 60 films by comparing the Photoconductivity (carrier generation and carrier transport) of the conducting polymer sensitized with C 60 with that of the conducting polymer alone. We present time-resolved transient PC results, subnanosecond to 0.5 μs, obtained from poly[2-methoxy,5-(2'-ethyl-hexyloxy)-p-phenylene vinylene] (MEH-PPV) and poly(3-octylthiophene) (P3OT), and from conducting polymer films sensitized with several concentrations of C 60

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