The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

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

  • ab initio study of electron mean free paths and thermoelectric properties of lead telluride
    Materials Today Physics, 2017
    Co-Authors: Qichen Song, Jiawei Zhou, Zhiwei Ding, Gang Chen
    Abstract:

    Abstract Last few years have witnessed significant enhancement of thermoelectric figure of merit of lead telluride (PbTe) via nanostructuring. Despite the experimental progress, current understanding of the electron transport in PbTe is based on either band structure calculation using first principles with constant relaxation time approximation or empirical models, both relying on adjustable parameters obtained by fitting experimental data. Here, we report parameter-free first-principles calculation of electron and phonon transport properties of PbTe, including mode-by-mode Electron-Phonon Scattering analysis, leading to detailed information on electron mean free paths and the contributions of electrons and phonons with different mean free paths to thermoelectric transport properties in PbTe. Such information will help to rationalize the use and optimization of nanostructures to achieve high thermoelectric figure of merit.

  • first principles mode by mode analysis for electron phonon Scattering channels and mean free path spectra in gaas
    Physical Review B, 2017
    Co-Authors: Tehuan Liu, Bolin Liao, Jiawei Zhou, David J Singh, Gang Chen
    Abstract:

    We present a first-principles framework to investigate the electron Scattering channels and transport properties for polar materials by combining the exact solution of the linearized Electron-Phonon (e-ph) Boltzmann transport equation in its integral-differential form associated with the e-ph coupling matrices obtained from the polar Wannier interpolation scheme. No ad hoc parameter is required throughout this calculation, and GaAs, a well-studied polar material, is used as an example to demonstrate this method. In this work, the long-range and short-range contributions as well as the intravalley and intervalley transitions in the e-ph interactions (EPIs) have been quantitatively addressed. Promoted by such mode-by-mode analysis, we find that in GaAs, the piezoelectric Scattering is comparable to deformation-potential Scattering for electron Scatterings by acoustic phonons in EPI even at room temperature, and it makes a significant contribution to mobility. Furthermore, we achieved good agreement with experimental data for the mobility, and we identified that electrons with mean free paths between 130 and 210 nm provide the dominant contribution to the electron transport at 300 K. Such information provides a deeper understanding of the electron transport in GaAs, and the presented framework can be readily applied to other polar materials.

  • first principles mode by mode analysis for electron phonon Scattering channels and mean free path spectra in gaas
    Physical Review Letters, 2017
    Co-Authors: David J Singh, Bolin Liao, Jiawei Zhou, Tehuan Liu, Gang Chen
    Abstract:

    United States. Dept. of Energy. Office of Basic Energy Sciences (Energy Frontiers Research Center. Award DE-FG02-09ER46577)

  • ab initio study of electron phonon interaction in phosphorene
    Physical Review B, 2015
    Co-Authors: Bolin Liao, Jiawei Zhou, Bo Qiu, Mildred S Dresselhaus, Gang Chen
    Abstract:

    The monolayer of black phosphorous, or phosphorene, has recently emerged as a new 2D semiconductor with intriguing highly anisotropic transport properties. Existing calculations of its intrinsic phonon-limited electronic transport properties so far rely on the deformation potential approximation, which is in general not directly applicable to anisotropic materials since the deformation along one specific direction can scatter electrons traveling in all directions. We perform a first-principles calculation of the Electron-Phonon interaction in phosphorene based on density functional perturbation theory and Wannier interpolation. Our calculation reveals that 1) the high anisotropy provides extra phase space for Electron-Phonon Scattering, and 2) optical phonons have appreciable contributions. Both effects cannot be captured by the deformation potential calculations.

Jelena Sjakste - One of the best experts on this subject based on the ideXlab platform.

  • wannier interpolation of the electron phonon matrix elements in polar semiconductors polar optical coupling in gaas
    Physical Review B, 2015
    Co-Authors: Jelena Sjakste, Nathalie Vast, Matteo Calandra, Francesco Mauri
    Abstract:

    A new computational method is introduced that allows interpolation of the Electron-Phonon matrix elements in the space of localized Wannier functions, extending a previous method for study of polar semiconductors. The amount of broadening of the bands in GaAs due to Electron-Phonon Scattering is presented, showing good agreement with experimental results. The method is shown to perform better than an empirical pseudopotential.

  • ab initio calculation of electron phonon Scattering time in germanium
    Physical Review B, 2011
    Co-Authors: Valeriy Tyuterev, Nathalie Vast, Sergey Obukhov, Jelena Sjakste
    Abstract:

    The intervalley Scattering time in n-type germanium from thevalley to the L, � ,a ndX valleys, has been computed ab initio with a method based on the density functional perturbation theory. We demonstrate that the pressure dependence of the lifetime of the exciton limited by the Electron-Phonon interaction is well described. Moreover, we discuss relaxation times measured by various pump-probe experiments at low and ambient temperatures. The contributions of the various phonons to the Scattering are computed. Relaxation times due to the Electron-Phonon coupling are provided for each intervalley transition, as well as their behavior under pressure.

  • ab initio method for calculating electron phonon Scattering times in semiconductors application to gaas and gap
    Physical Review Letters, 2007
    Co-Authors: Jelena Sjakste, Nathalie Vast, Valeriy Tyuterev
    Abstract:

    We propose a fully ab initio approach to calculate Electron-Phonon Scattering times for excited electrons interacting with short-wavelength (intervalley) phonons in semiconductors. Our approach is based on density functional perturbation theory and on the direct integration of electronic Scattering probabilities over all possible final states with no ad hoc assumptions. We apply it to the deexcitation of hot electrons in GaAs, and calculate the lifetime of the direct exciton in GaP, both in excellent agreement with experiments. Matrix elements of the Electron-Phonon coupling, and their dependence on the wave vector of the final state and on the phonon modes, are shown to be crucial ingredients of the evaluation of Electron-Phonon Scattering times.

J D Meindl - One of the best experts on this subject based on the ideXlab platform.

  • physical modeling of temperature coefficient of resistance for single and multi wall carbon nanotube interconnects
    IEEE Electron Device Letters, 2007
    Co-Authors: Azad Naeemi, J D Meindl
    Abstract:

    Equivalent circuit models are presented for the resistance of single- and multi-wall carbon nanotubes (MWCNs) that capture various Electron-Phonon Scattering mechanisms as well as changes in the number of conduction channels as a function of temperature. For single- and few-wall nanotubes, the temperature coefficient of resistance (TCR) is always positive and increases with length. It reaches 1/(T-200 K) for lengths much larger than the electron mean free path, where T is the temperature in kelvin. For MWCNs with large diameters (>20 nm), TCR varies from -1/T to +0.66/(T-200 K) as the length varies from zero to very large values

  • impact of electron phonon Scattering on the performance of carbon nanotube interconnects for gsi
    IEEE Electron Device Letters, 2005
    Co-Authors: Azad Naeemi, J D Meindl
    Abstract:

    While electron mean-free path in carbon nanotubes can be as large as several micrometers for small bias voltages, for large biases electrons get backscattered by optical and zone-boundary phonons and nanotube resistance can increase by more than 100 times. This letter reveals this kind of backScattering has a small impact (error <25%) in most interconnect applications of carbon nanotubes in which adequate numbers of nanotubes are connected in parallel. This is mainly due to relatively small electric fields along nanotubes when they are used as interconnects. This is in sharp contrast with transistor applications of carbon nanotubes in which transconductance degrades considerably by Electron-Phonon Scatterings unless their channels are made ultrashort (/spl sim/10 nm).

Jiawei Zhou - One of the best experts on this subject based on the ideXlab platform.

  • ab initio study of electron mean free paths and thermoelectric properties of lead telluride
    Materials Today Physics, 2017
    Co-Authors: Qichen Song, Jiawei Zhou, Zhiwei Ding, Gang Chen
    Abstract:

    Abstract Last few years have witnessed significant enhancement of thermoelectric figure of merit of lead telluride (PbTe) via nanostructuring. Despite the experimental progress, current understanding of the electron transport in PbTe is based on either band structure calculation using first principles with constant relaxation time approximation or empirical models, both relying on adjustable parameters obtained by fitting experimental data. Here, we report parameter-free first-principles calculation of electron and phonon transport properties of PbTe, including mode-by-mode Electron-Phonon Scattering analysis, leading to detailed information on electron mean free paths and the contributions of electrons and phonons with different mean free paths to thermoelectric transport properties in PbTe. Such information will help to rationalize the use and optimization of nanostructures to achieve high thermoelectric figure of merit.

  • first principles mode by mode analysis for electron phonon Scattering channels and mean free path spectra in gaas
    Physical Review B, 2017
    Co-Authors: Tehua Liu, Jiawei Zhou, David J Singh, Oli Liao, Gang Che
    Abstract:

    We present a first-principles framework to investigate the electron Scattering channels and transport properties for polar material by combining the exact solution of linearized Electron-Phonon (e-ph) Boltzmann transport equation in its integral-differential form associated with the e-ph coupling matrices obtained from polar Wannier interpolation scheme. No ad hoc parameter is required throughout this calculation, and GaAs, a well-studied polar material, is used as an example to demonstrate this method. In this work, the long-range and short-range contributions as well as the intravalley and intervalley transitions in the e-ph interactions (EPIs) have been quantitatively addressed. Promoted by such mode-by-mode analysis, we find that in GaAs, the piezoelectric Scattering is comparable to deformation-potential Scattering for electron Scatterings by acoustic phonons in EPI even at room temperature and makes a significant contribution to mobility. Furthermore, we achieved good agreements with experimental data for the mobility, and identified that electrons with mean free paths between 130 and 210 nm contribute dominantly to the electron transport at 300 K. Such information provides deeper understandings on the electron transport in GaAs, and the presented framework can be readily applied to other polar materials.

  • first principles mode by mode analysis for electron phonon Scattering channels and mean free path spectra in gaas
    Physical Review B, 2017
    Co-Authors: Tehuan Liu, Bolin Liao, Jiawei Zhou, David J Singh, Gang Chen
    Abstract:

    We present a first-principles framework to investigate the electron Scattering channels and transport properties for polar materials by combining the exact solution of the linearized Electron-Phonon (e-ph) Boltzmann transport equation in its integral-differential form associated with the e-ph coupling matrices obtained from the polar Wannier interpolation scheme. No ad hoc parameter is required throughout this calculation, and GaAs, a well-studied polar material, is used as an example to demonstrate this method. In this work, the long-range and short-range contributions as well as the intravalley and intervalley transitions in the e-ph interactions (EPIs) have been quantitatively addressed. Promoted by such mode-by-mode analysis, we find that in GaAs, the piezoelectric Scattering is comparable to deformation-potential Scattering for electron Scatterings by acoustic phonons in EPI even at room temperature, and it makes a significant contribution to mobility. Furthermore, we achieved good agreement with experimental data for the mobility, and we identified that electrons with mean free paths between 130 and 210 nm provide the dominant contribution to the electron transport at 300 K. Such information provides a deeper understanding of the electron transport in GaAs, and the presented framework can be readily applied to other polar materials.

  • first principles mode by mode analysis for electron phonon Scattering channels and mean free path spectra in gaas
    Physical Review Letters, 2017
    Co-Authors: David J Singh, Bolin Liao, Jiawei Zhou, Tehuan Liu, Gang Chen
    Abstract:

    United States. Dept. of Energy. Office of Basic Energy Sciences (Energy Frontiers Research Center. Award DE-FG02-09ER46577)

  • ab initio study of electron phonon interaction in phosphorene
    Physical Review B, 2015
    Co-Authors: Bolin Liao, Jiawei Zhou, Bo Qiu, Mildred S Dresselhaus, Gang Chen
    Abstract:

    The monolayer of black phosphorous, or phosphorene, has recently emerged as a new 2D semiconductor with intriguing highly anisotropic transport properties. Existing calculations of its intrinsic phonon-limited electronic transport properties so far rely on the deformation potential approximation, which is in general not directly applicable to anisotropic materials since the deformation along one specific direction can scatter electrons traveling in all directions. We perform a first-principles calculation of the Electron-Phonon interaction in phosphorene based on density functional perturbation theory and Wannier interpolation. Our calculation reveals that 1) the high anisotropy provides extra phase space for Electron-Phonon Scattering, and 2) optical phonons have appreciable contributions. Both effects cannot be captured by the deformation potential calculations.

T J B M Janssen - One of the best experts on this subject based on the ideXlab platform.

  • clock controlled emission of single electron wave packets in a solid state circuit
    Physical Review Letters, 2013
    Co-Authors: J D Fletcher, H Howe, M Pepper, S P Giblin, J Griffiths, G A C Jones, I Farrer, D A Ritchie, T J B M Janssen, M Kataoka
    Abstract:

    : We demonstrate the energy- and time-resolved detection of single-electron wave packets from a clock-controlled source transmitted through a high-energy quantum Hall edge channel. A quantum dot source is loaded with single electrons which are then emitted ~150 meV above the Fermi energy. The energy spectroscopy of emitted electrons indicates that at high magnetic field these electrons can be transported over several microns without inelastic electron-electron or Electron-Phonon Scattering. Using a time-resolved spectroscopic technique, we deduce the wave packet size at picosecond resolution. We also show how this technique can be used to switch individual electrons into different electron waveguides (edge channels).

  • Clock-controlled emission of single-electron wave packets in a solid-state circuit.
    Physical review letters, 2013
    Co-Authors: J D Fletcher, H Howe, M Pepper, S P Giblin, J Griffiths, G A C Jones, I Farrer, D A Ritchie, Patrick See, T J B M Janssen
    Abstract:

    We demonstrate the energy- and time-resolved detection of single-electron wave packets from a clock-controlled source transmitted through a high-energy quantum Hall edge channel. A quantum dot source is loaded with single electrons which are then emitted $\ensuremath{\sim}150\text{ }\text{ }\mathrm{meV}$ above the Fermi energy. The energy spectroscopy of emitted electrons indicates that at high magnetic field these electrons can be transported over several microns without inelastic electron-electron or Electron-Phonon Scattering. Using a time-resolved spectroscopic technique, we deduce the wave packet size at picosecond resolution. We also show how this technique can be used to switch individual electrons into different electron waveguides (edge channels).