Hot Carrier Relaxation by Extreme Electron-LO Phonon Scattering in GaN

Heß, Sebastian; Taylor, Robert A.; O'Sullivan, E.D; Ryan, John F.; Cain, N.; Roberts, Victoria A.; Roberts, J.S.

doi:10.1002/(sici)1521-3951(199911)216:1<51::aid-pssb51>3.0.co;2-m

Cited by 7 publications

(6 citation statements)

References 5 publications

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“…5, we plot the anharmonic decay time τ A as a function of temperature as derived from the Raman FWHM using Eq. (6). The anharmonic decay time shows a sizable increase at lower temperatures, where a substantial fraction of the Raman linewidth is given by the background term 0 .…”

Section: E Lo Phonon Lifetimesupporting

confidence: 77%

“…At high current densities, the energy loss of hot electrons to the lattice gives rise to self-heating effects which are deleterious to device performance. In polar lattices, hot-carrier relaxation takes place primarily by emission of zone-center longitudinaloptical (LO) phonons via Fröhlich interaction [6]. Depending on the LO phonon lifetimes, a nonequilibrium hot-phonon population may build up, leading to phonon reabsorption and a reduction of the carrier energy-loss rate.…”

Section: Introductionmentioning

confidence: 99%

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Anharmonic phonon decay in cubic GaN

et al. 2015

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We present a Raman-scattering study of optical phonons in zinc-blende (cubic) GaN for temperatures ranging from 80 to 750 K. The experiments were performed on high-quality, cubic GaN films grown by molecular-beam epitaxy on GaAs (001) substrates. The observed temperature dependence of the optical phonon frequencies and linewidths is analyzed in the framework of anharmonic decay theory, and possible decay channels are discussed in the light of density-functional-theory calculations. The longitudinal-optical (LO) mode relaxation is found to occur via asymmetric decay into acoustic phonons, with an appreciable contribution of higher-order processes. The transverse-optical mode linewidth shows a weak temperature dependence and its frequency downshift is primarily determined by the lattice thermal expansion. The LO phonon lifetime is derived from the observed Raman linewidth and an excellent agreement with previous theoretical predictions is found.

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Section: E Lo Phonon Lifetimesupporting

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Anharmonic phonon decay in cubic GaN

et al. 2015

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“…This is because the carrier density is tunable in the same sample by adjusting the optical delay between pump and probe beams. Although there have been a few reports on femtosecond transient absorption spectroscopy in GaN epilayers, [13][14][15] they are mainly related to the ultrafast carrier dynamics related to the energy transfer to the bottom of the band. Photoinduced absorption in GaN/AlGaN single quantum well ͑SQW͒ due to internal and built-in electric fields has been reported by employing degenerate pump-andprobe ͑P&P͒ experiments at room temperature.…”

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confidence: 99%

Effects of internal electric field and carrier density on transient absorption spectra in a thin GaN epilayer

et al. 2002

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Carrier dynamics in a thin GaN epilayer with a thickness of 0.15 m almost coherently grown on Al 0.2 Ga 0.8 N was investigated using transient absorption spectroscopy above and below the band gap. The absorption peak of excitons was observed at 3.521 eV without a pump beam. Just after the photoexcitation above the band gap, the bleaching occurred and the absorption peak of excitons disappeared due to highdensity photogenerated carriers. At about 30 ps, the absorption peak was restored at 3.527 eV, as the carriers were decreased owing to radiative and/or nonradiative recombination. After that, the absorption spectra were larger than that without a pump beam. This is because excitonic absorption suppressed by both Franz-Keldysh and Stark effects is restored by photoinduced carriers as a result of the screening of the internal electric field.

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“…1 c, d. It is known that the carrier cooling occurs mainly by scattering with optical phonons [24,53,54].…”

Section: Temperature Quasi Fermi-energymentioning

confidence: 99%

Ultrafast dynamics of hot charge carriers in an oxide semiconductor probed by femtosecond spectroscopic ellipsometry

Richter,

Herrfurth,

Espinoza

et al. 2019

Preprint

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Many linked processes occur concurrently in strongly excited semiconductors, such as interband and intraband absorption, scattering of electrons and holes by the heated lattice, Pauli blocking, bandgap renormalization and the formation of Mahan excitons. In this work, we disentangle their dynamics and contributions to the optical response of a ZnO thin film. Using our unique setup for broadband pump-probe ellipsometry, we directly and unambiguously obtain the real and imaginary part of the transient dielectric function which we compare with first-principles simulations. The interband and excitonic absorption are partially blocked and screened by the photo-excited electron occupation of the conduction band and hole occupation of the valence band. Simultaneously, intra-valence-band transitions occur at sub-picosecond time scales after holes scatter to the edge of the Brillouin zone. Our results pave new ways for the understanding of non-equilibrium charge-carrier dynamics in materials by reliably distinguishing between changes in absorption coefficient and refractive index, thereby separating competing processes. This information will help to overcome the limitations of materials for high-power optical devices that owe their properties from dynamics in the ultrafast regime.

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Hot Carrier Relaxation by Extreme Electron-LO Phonon Scattering in GaN

Cited by 7 publications

References 5 publications

Anharmonic phonon decay in cubic GaN

Anharmonic phonon decay in cubic GaN

Effects of internal electric field and carrier density on transient absorption spectra in a thin GaN epilayer

Ultrafast dynamics of hot charge carriers in an oxide semiconductor probed by femtosecond spectroscopic ellipsometry

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