Nonequilibrium dynamics of photoexcited electrons in graphene: Collinear scattering, Auger processes, and the impact of screening

Tomadin, Andrea; Brida, Daniele; Cerullo, Giulio; Ferrari, Andrea C.; Polini, Marco

doi:10.1103/physrevb.88.035430

Cited by 180 publications

(248 citation statements)

References 124 publications

(271 reference statements)

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“…This is followed by ultrafast (<50 fs) electron heating, which creates a quasi-equilibrium distribution that can be described by an increased electron temperature. The details of this heating process have been addressed in a number of experimental [22,23,26,27,[29][30][31][32][33] and theoretical [24,25,28,42,43] studies. The system returns to its original (pre-photoexcitation) state through cooling of the hot electrons, which can occur through interaction with graphene lattice optical or acoustic phonons, and substrate phonons [12,17,28,[44][45][46].…”

Section: Time-resolved Photocurrentmentioning

confidence: 99%

Hot-carrier photocurrent effects at graphene–metal interfaces

Tielrooij¹,

Massicotte²,

Piątkowski³

et al. 2015

J. Phys.: Condens. Matter

100

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Photoexcitation of graphene leads to an interesting sequence of phenomena, some of which can be exploited in optoelectronic devices based on graphene. In particular, the efficient and ultrafast generation of an electron distribution with an elevated electron temperature and the concomitant generation of a photo-thermoelectric voltage at symmetry-breaking interfaces is of interest for photosensing and light harvesting. Here, we experimentally study the generated photocurrent at the graphene-metal interface, focusing on the time-resolved photocurrent, the effects of photon energy, Fermi energy and light polarization. We show that a single framework based on photo-thermoelectric photocurrent generation explains all experimental results.

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Section: Time-resolved Photocurrentmentioning

confidence: 99%

Hot-carrier photocurrent effects at graphene–metal interfaces

Tielrooij¹,

Massicotte²,

Piątkowski³

et al. 2015

J. Phys.: Condens. Matter

100

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show abstract

“…58, 63 Subsequently, this distribution thermalizes through e−ph scattering toward a hot Fermi−Dirac distribution, 12,58−65 with the time scale in the range of hundreds of fs (τ 1 ). 12,58−63 Finally, the hot Fermi−Dirac distribution relaxes to equilibrium by e−h recombination, which can lead to plasmon emission, phonon emission, and Auger scattering on a ps time scale (τ 2 ).…”

mentioning

confidence: 99%

Photothermoelectric and Photoelectric Contributions to Light Detection in Metal–Graphene–Metal Photodetectors

et al. 2014

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Graphene's high mobility and Fermi velocity, combined with its constant light absorption in the visible to far-infrared range, make it an ideal material to fabricate high-speed and ultrabroadband photodetectors. However, the precise mechanism of photodetection is still debated. Here, we report wavelength and polarization-dependent measurements of metal−graphene−metal photodetectors. This allows us to quantify and control the relative contributions of both photothermo-and photoelectric effects, both adding to the overall photoresponse. This paves the way for a more efficient photodetector design for ultrafast operating speeds.KEYWORDS: Graphene, photodetectors, Raman spectroscopy, photoresponse, optoelectronics T he unique optical and electronic properties of graphene make it ideal for photonics and optoelectronics. 1 A variety of prototype devices have already been demonstrated, such as transparent electrodes in displays 2 and photovoltaic modules, 3 optical modulators, 4 plasmonic devices, 4−9 microcavities, 10,11 and ultrafast lasers. 12 Among these, a significant effort is being devoted to photodetectors (PDs). 6,10,11,13−25 Various photodetection schemes and architectures have been proposed to date. The simplest configuration is the metal− graphene−metal (MGM) PD, in which graphene is contacted with metal electrodes as the source and drain. 13−18 These PDs can be combined with metal nanostructures enabling local surface plasmons and increased absorption, realizing an enhancement in responsivity (i.e., the ratio of the lightgenerated electrical current to the incident light power). 6,26 Microcavity based PDs were also used, with increased light absorption at the cavity resonance frequency, again achieving an increase in responsivity. 10,11 Another scheme is the integration of graphene with a waveguide to increase the effective interaction length with light. 25,27 Hybrid approaches employ semiconducting nanodots as light-absorbing media. 22 In this case, light excites electron−hole (e−h) pairs in the nanodots; the electrons are trapped in the nanodot, while the holes are transferred to graphene, thus effectively gating it. 22 Under applied drain−source bias, this results in a shift in the Dirac point, thus a modulation of the drain−source current. 22 Due to the long trapping time of the electrons within the dot, the transferred holes can cycle many times through the phototransistor before relaxation and e−h recombination. This gives a photoconductive gain; i.e., one absorbed photon effectively results in an electrical current of several electrons. Responsivities >10 7 A/W were reported, 22 but with a millisecond time scale, not suitable for, e.g., high-speed optical communications. Devices were also fabricated for detection of THz light. 28,29 In this low energy range, Pauli blocking forbids the direct excitation of e−h pairs due to finite doping. Instead, an antenna coupled to source and gate of the device excites plasma waves within the channel. These are rectified, leading to a detectable dc out...

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“…This kinematic peculiarity results in a singular contribution to the collision integral [4,6,8,11,14,15] allowing for a nonperturbative solution to the kinetic equation. A distinct feature of this solution is fast unidirectional thermalization [11] that facilitates integration of the kinetic equation.…”

Section: Introductionmentioning

confidence: 99%

Hydrodynamics in graphene: Linear-response transport

et al. 2015

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We develop a hydrodynamic description of transport properties in graphene-based systems, which we derive from the quantum kinetic equation. In the interaction-dominated regime, the collinear scattering singularity in the collision integral leads to fast unidirectional thermalization and allows us to describe the system in terms of three macroscopic currents carrying electric charge, energy, and quasiparticle imbalance. Within this "three-mode" approximation, we evaluate transport coefficients in monolayer graphene as well as in double-layer graphene-based structures. The resulting classical magnetoresistance is strongly sensitive to the interplay between the sample geometry and leading relaxation processes. In small, mesoscopic samples, the macroscopic currents are inhomogeneous, which leads to a linear magnetoresistance in classically strong fields. Applying our theory to double-layer graphene-based systems, we provide a microscopic foundation for a phenomenological description of giant magnetodrag at charge neutrality and find the magnetodrag and Hall drag in doped graphene.

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Nonequilibrium dynamics of photoexcited electrons in graphene: Collinear scattering, Auger processes, and the impact of screening

Cited by 180 publications

References 124 publications

Hot-carrier photocurrent effects at graphene–metal interfaces

Hot-carrier photocurrent effects at graphene–metal interfaces

Photothermoelectric and Photoelectric Contributions to Light Detection in Metal–Graphene–Metal Photodetectors

Hydrodynamics in graphene: Linear-response transport

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