Phonon focusing effect on thermal conductivity of hexagonal group III-nitrides and silicon carbide crystals

Publication date: Available online 7 November 2019Source: Physics Letters AAuthor(s): D.A. Chernodoubov, A.V. InyushkinAbstractThermal conductivity κ of 4H-, 6H-SiC and wurtzite GaN, InN, AlN crystals is calculated accounting phonon focusing effect at low temperatures with only diffusive phonon boundary scattering. The orientation dependence of thermal conductivity is similar in these materials. Thermal conductivity is enhanced in the direction of approximately 45∘ to the c axis up to 27% for GaN, 24% for 6H-SiC, 32% for InN, and 9% for AlN compared to the isotropic case for the circular cross-section and finite-length samples. Contributions of transverse T1 and T2 modes are nearly the same, about 40–45%, while the focusing of T2 mode contributes essentially to the angular dependence of κ. We find that the phonon focusing does not change κ value (within 5%) in the direction of 60∘ to the c axis in all hexagonal crystals studied so far.

Source: Physics Letters A - November 9, 2019 Category: Physics Source Type: research