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

A. Vega-Flick, D. Jung, S. Yue, J. E. Bowers, and B. Liao
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Lens 2 of TTG setup with optical heterodyne detection
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Physical Review Materials
3, 034603

Epitaxial growth of III-V semiconductors on Si is a promising route for silicon photonics. Threading dislo- cations 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 noncontact laser-induced transient thermal grating technique with ab initiophonon 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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Epitaxial Growth on Si