Reduced thermal conductivity of epitaxial GaAsSb on InP due to lattice mismatch induced biaxial strain

High-quality lattice-matched and mismatched strained GaAs1−xSbx (0.37 < x < 0.57) sub-micrometer epilayers are grown on InP by molecular beam epitaxy. Based on a heat conduction model regarding the heat transfer process between the thin GaAsSb films and thick InP substrates, the corresponding thermal conductivity of GaAsSb epilayers was accurately extracted from the power and temperature micro-Raman measurement. Combined with time-domain thermoreflectance measurements, we found that in comparison to the lattice-matched sample with Sb = 47.7%, a significant reduction in thermal conductivity of the lattice-mismatched sample with Sb = 37.9% and Sb = 56.2% is observed. With the help of diffraction reciprocal space maps and temperature-dependent photoluminescence results, the reduction in thermal conductivity is attributed to lattice-mismatch-induced biaxial tensile and compressive strain that can cause the breakage of the cubic crystal symmetry and provoke more defects.