<i>Ab initio</i> study of the effects of pressure and strain on electron–phonon coupling in IV and III–V semiconductors

Sjakste, Jelena; Vast, Nathalie; Jani, Hariom; Obukhov, S. V.; Tyuterev, V. G.

doi:10.1002/pssb.201200526

Cited by 9 publications

(4 citation statements)

References 26 publications

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“…It is known that high crystal symmetry imposes selection rules on the scattering matrix elements and limits the possible channels of phonon scattering [40]. In particular, this symmetry-breaking strain effect on electronphonon scattering in Si and III-V semiconductors has been studied and well understood [41][42][43][44] and the same principle also applies to phonon-phonon scattering. To confirm that the observed significant reduction of thermal conductivity in this work originates from the symmetrybreaking biaxial strain, we also conducted ab initio thermal conductivity calculation of GaAs under an isotropic tensile stress of 250 MPa, where the reduction of thermal conductivity was found to be within 2%.…”

Section: Resultsmentioning

confidence: 99%

Reduced thermal conductivity of epitaxial GaAs on Si due to symmetry-breaking biaxial strain

Vega-Flick

Jung

Yue

et al. 2019

Phys. Rev. Materials

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Epitaxial growth of III-V semiconductors on Si is a promising route for silicon photonics. Threading dislocations and the residual thermal stress generated during growth are expected to affect the thermal conductivity of the III-V semiconductors, which is crucial for efficient heat dissipation from photonic devices built on this platform. In this work, we combine a non-contact laser-induced transient thermal grating technique with ab initio phonon simulations to investigate the in-plane thermal transport of epitaxial GaAs-based buffer layers on Si, employed in the fabrication of III-V quantum dot lasers. Surprisingly, we find a significant reduction of the in-plane thermal conductivity of GaAs, up to 19%, as a result of a small in-plane biaxial stress of ∼250 MPa. Using ab initio phonon calculations, we attribute this effect to the enhancement of phonon-phonon scattering caused by the in-plane biaxial stress, which breaks the cubic crystal symmetry of GaAs. Our results indicate the importance of eliminating the residual thermal stress in the epitaxial III-V layers on Si to avoid the reduction of thermal conductivity and facilitate heat dissipation. Additionally, our results showcase potential means of effectively controlling thermal conductivity of solids with external strain/stress.

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Section: Resultsmentioning

confidence: 99%

Reduced thermal conductivity of epitaxial GaAs on Si due to symmetry-breaking biaxial strain

Vega-Flick

Jung

Yue

et al. 2019

Phys. Rev. Materials

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“…The discrepancy of el-ph coupling constant λ to that of Brorson's measurement could be due to probe wavelength, or the differences of strain in epitaxially grown copper and polycrystalline copper [40,41], or substrates [30], or a combination thereof. In our measurement the probe wavelength was set to 609 nm, ensuring that the thermalized electron contribution dominates in the transient reflectivity signal, while Brorson et al [19] used the 630-nm probe wavelength for their measurement.…”

Section: F El-ph Coupling and Electron Internal Thermalization Analysismentioning

confidence: 85%

Experimental study of electron-phonon coupling and electron internal thermalization in epitaxially grown ultrathin copper films

Shen

Timalsina

et al. 2015

Phys. Rev. B

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Electron interaction in nanoscale metal structures is of major interest in understanding and designing nanoscale electronic devices. In this study, electron interaction in epitaxially grown 20-nm-thick copper film on Si(100) was studied using femtosecond pump-probe technique with tunable probe photon energy near the d-band to Fermi-level transition. It was found that probe-photon-energy dependence on the transient reflectivity signal can be divided into four regimes, and the borders of these regimes depend on the pump power. Based on a phenomenological model, the excited electrons were separated into nonthermalized and thermalized electrons, and it was seen that the probe-photon-energy dependence of the signal can be explained by the difference of the ratios of nonthermalized to thermalized electron components. Furthermore, it was found that each of these two components can be selectively excited by properly choosing the probe photon energy. Each electron-phonon (el-ph) coupling and electron internal thermalization time were investigated individually without interference from each other's processes. We show that el-ph coupling factor is larger in epitaxial copper film than the previously reported value in polycrystalline-copper film. In addition, the electron internal thermalization time is smaller than the reported value for the polycrystalline gold and silver films.

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“…Strain affects mostly the scattering by acoustic phonons, 19,20 while it has little effect on inter-valley scattering and scattering by optical phonons. 19,35 Here we are chiefly concerned with n-type carrier thermoelectric properties. However, at high temperatures some p-type transport needs to be considered to fully account for the bi-polar behaviour.…”

Section: Fig 2 Energy Gap Between the E ∆ 3vmentioning

confidence: 99%

Enhancement of the electronic thermoelectric properties of bulk strained silicon-germanium alloys using the scattering relaxation times from first-principles calculations

Murphy-Armando

2019

Journal of Applied Physics

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We use first-principles electronic structure methods to calculate the electronic thermoelectric properties (i.e. due to electronic transport only) of single-crystalline bulk n-type silicon-germanium alloys vs Ge composition, temperature, doping concentration and strain. We find excellent agreement to available experiments for the resistivity, mobility and Seebeck coefficient. These results are combined with the experimental lattice thermal conductivity to calculate the thermoelectric figure of merit ZT , finding very good agreement with experiment. We predict that 3% tensile hydrostatic strain enhances the n-type ZT by 50% at carrier concentrations of n = 10 20 cm −3 and temperature of T = 1200K. These enhancements occur at different alloy compositions due to different effects: at 50% Ge composition the enhancements are achieved by a strain induced decrease in the Lorenz number, while the power factor remains unchanged. These characteristics are important for highly doped and high temperature materials, in which up to 50% of the heat is carried by electrons. At 70% Ge the increase in ZT is due to a large increase in electrical conductivity produced by populating the high mobility Γ conduction band valley, lowered in energy by strain.

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Ab initio study of the effects of pressure and strain on electron–phonon coupling in IV and III–V semiconductors

Cited by 9 publications

References 26 publications

Reduced thermal conductivity of epitaxial GaAs on Si due to symmetry-breaking biaxial strain

Reduced thermal conductivity of epitaxial GaAs on Si due to symmetry-breaking biaxial strain

Experimental study of electron-phonon coupling and electron internal thermalization in epitaxially grown ultrathin copper films

Enhancement of the electronic thermoelectric properties of bulk strained silicon-germanium alloys using the scattering relaxation times from first-principles calculations

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