Effect of Heating and Cooling of Photogenerated Electron–Hole Plasma in Optically Pumped Graphene on Population Inversion

Ryzhii, V.; Ryzhii, M.; Mitin, Vladimir; Satou, Akira; Otsuji, T.

doi:10.1143/jjap.50.094001

Cited by 38 publications

(34 citation statements)

References 49 publications

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“…The rate of the optical phonon-assisted interband transitions (recombination rate) R inter 0 and the rate of the intraband energy relaxation associated with optical phonons R intra 0 can be calculated using the following simplified formulas [9,16] (see, also Ref. [20]:…”

Section: Equations Of the Modelmentioning

confidence: 99%

“…The η 0 − µ and η 0 − T dependences are associated with the linearity of the density of states in GLs as a function of energy. To a good approximation these dependences can be described [16] by function (10) is given by…”

Section: Equations Of the Modelmentioning

confidence: 99%

“…This in part can be realized in the case of optical pumping with Ω 0 /2 < ω 0 ' [16] . Taking into account that in GLs ω 0 ≃ 0.2 eV, in the case of CO 2 laser as a pumping source, Ω 0 /ω 0 ≃ 0.5.…”

Section: Introductionmentioning

confidence: 99%

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Toward the creation of terahertz graphene injection laser

Ryzhii

Mitin

et al. 2011

Journal of Applied Physics

146

117

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We study the effect of population inversion associated with the electron and hole injection in graphene p-i-n structures at the room and slightly lower temperatures. It is assumed that the recombination and energy relaxation of electrons and holes is associated primarily with the interband and intraband processes assisted by optical phonons. The dependences of the electron-hole and optical phonon effective temperatures on the applied voltage, the current-voltage characteristics, and the frequency-dependent dynamic conductivity are calculated. In particular, we demonstrate that at low and moderate voltages the injection can lead to a pronounced cooling of the electron-hole plasma in the device i-section to the temperatures below the lattice temperature. However at higher voltages, the voltage dependences can be ambiguous exhibiting the S-shape. It is shown that the frequency-dependent dynamic conductivity can be negative in the terahertz range of freqiencies at certain values of the applied voltage. The electron-hole plasma cooling substantially reinforces the effect of negative dynamic conductivity and promotes the realization of terahertz lasing. On the other hand, the heating of optical phonon system can also be crucial affecting the realization of negative dynamic conductivity and terahertz lasing at the room temperatures.

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Section: Equations Of the Modelmentioning

confidence: 99%

Section: Equations Of the Modelmentioning

confidence: 99%

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Toward the creation of terahertz graphene injection laser

Ryzhii

Mitin

et al. 2011

Journal of Applied Physics

146

117

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“…In the case of strong pumping, the effective temperature of the electron-hole plasma can be much higher than the lattice temperature [23]. As a result, the electron-hole plasma can become nondegenerate, so that µ e = µ < 0 while µ h = −µ > 0.…”

mentioning

confidence: 99%

“…In the case of pumping of intrinsic GLs, µ e = −µ h = µ = 0. In the latter case, T can differ from the lattice temperature T l being both higher than T l or lower [23].Considering in the following the case Σ d (x, y) = 0 and assuming that the fluctuations are not too strong (e|ϕ| < k B T ), Eq. (1) can be linearized: ∆ϕ = ϕ r s ln 1 + e µ/k B T − 4π e ae Σ i · δ(z),…”

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confidence: 99%

Tunneling recombination in optically pumped graphene with electron-hole puddles

Ryzhii

Otsuji

2011

Applied Physics Letters

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We evaluate recombination of electrons and holes in optically pumped graphene associated with the interband tunneling between electron-hole puddles and calculate the recombination rate and time. It is demonstrated that this mechanism can be dominant in a wide range of pumping intensities. We show that the tunneling recombination rate and time are nonmonotonic functions of the quasi-Fermi energies of electrons and holes and optical pumping intensity. This can result in hysteresis phenomena.The gapless energy spectrum of electrons and holes in graphene layers (GLs) and non-Bernal stacked multiple graphene layers (MGLs) [1][2][3], which leads to specific features of its electrical and optical processes, opens up prospects of building of novel devices exploiting the interband absorption and emission of terahertz (THz) and infrared (IR) photons. Apart from an obvious possibility to use of graphene in THz and IR photodetectors [4][5][6], graphene layers (GLs) and multiple graphene layers (MGLs) can serve as active media in THz or IR lasers with optical [7][8][9][10][11][12] and injection [13] pumping. The achievement of sufficiently strong population inversion, which is necessary for negative dynamic conductivity in the THz or IR ranges of frequencies, can be complicated by the recombination processes. The recombination of electrons and holes in GLs at not too low temperatures is mainly determined by the emission of optical photons [14]. Due to a relatively high energy of optical phonons ( ω 0 ≃ 0.2 eV), the recombination rate in GLs associated with this mechanism can be acceptable even at the room temperatures [10][11][12]. The radiative recombination in the practically interesting temperatures is weaker than that due to the optical phonon emission [15]. The acoustic phonon recombination mechanism as well as the Auger mechanism are forbidden due to the linearity of the electron and hole spectra even in the case their modifications associated with the inter-carrier interaction [16,17]. More complex processes involving the electron and hole scattering on impurities assisted by acoustic phonons also provide rather long recombination times which are longer than the radiative recombination time [18]. However in GLs with a disorder caused, for instance, by fluctuation of the surface charges resulting in the formation of the electron and hole puddles [19] (see also, for instance, Refs. [20][21][22]), the recombination can also be associated with the interband tunneling in the spots where the build-in fluctuation field is sufficiently strong.In this paper, we find the dependences of the recombination rate and time in graphene with electron-hole puddles on the quasi-Fermi energy of electrons and holes (pumping intensity). Our results can be used for the interpretation of experimental observations and to promote the realization of graphene-based THz and IR lasers.The electric potential ϕ = ϕ(x, y, z), where x and y are the coordinates in the GL plane and the coordinate z is directed perpendicular to this plane, is governed by ...

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Spectroscopic Study on Ultrafast Carrier Dynamics and Terahertz Amplified Stimulated Emission in Optically Pumped Graphene

Otsuji

Boubanga-Tombet

Satou

et al. 2012

J Infrared Milli Terahz Waves

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This paper reviews recent advances in spectroscopic study on ultrafast carrier dynamics and terahertz (THz) stimulated emission in optically pumped graphene. The gapless and linear energy spectra of electrons and holes in graphene can lead to nontrivial features such as negative dynamic conductivity in the THz spectral range, which may lead to the development of new types of THz lasers. First, the non-equilibrium carrier relaxation/ recombination dynamics is formulated to show how photoexcited carriers equilibrate their energy and temperature via carrier-carrier and carrier-phonon scatterings and in what photon energies and in what time duration the dynamic conductivity can take negative values as functions of temperature, pumping photon energy/intensity, and carrier relaxation rates. Second, we conduct time-domain spectroscopic studies using an optical pump and a terahertz probe with an optical probe technique at room temperature and show that graphene sheets amplify an incoming terahertz field. Two different types of samples are prepared for the measurement; one is an exfoliated monolayer graphene on SiO 2 /Si substrate and the other is a heteroepitaxially grown non-Bernal stacked multilayer graphene on a 3C-SiC/Si epi-wafer.

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Effect of Heating and Cooling of Photogenerated Electron–Hole Plasma in Optically Pumped Graphene on Population Inversion

Cited by 38 publications

References 49 publications

Toward the creation of terahertz graphene injection laser

Toward the creation of terahertz graphene injection laser

Tunneling recombination in optically pumped graphene with electron-hole puddles

Spectroscopic Study on Ultrafast Carrier Dynamics and Terahertz Amplified Stimulated Emission in Optically Pumped Graphene

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