Thermal diffusivity study in supported epitaxial InN thin films by the traveling-wave technique

摘要

High-quality crystalline (c) InN thin films have been obtained via gas-source molecular beam epitaxy, using hydrazoic acid (HN_3) precursor, on indium tin oxide/glass, c-sapphire, and c-GaN substrates at growth temperatures between 623 and 823 K. A systematic study of thermal diffusivity has been performed using the traveling-wave method. We report a high thermal diffusivity value of 0.55 cm~2/s for a combined 1.7 μm thick InN film grown on GaN substrates not observed before. X-ray diffraction data of InN grown on GaN substrates indicated lattice shrinkage with increasing thickness of the film that supports efficient phonon propagation and resulting higher thermal diffusivity. The latticcyibrational modes expressed in the Raman spectroscopic data corroborate the diffraction results. The thickness dependence of the thermal diffusivity has been modeled to estimate a bulk value of the essential thermal property.