  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.
