Thermal properties of In2O3 and α-Ga2S3 compounds

We investigate the thermal conductivity of In2O3 and alpha-Ga2S3 lattices using simulations based on the Boltzmann phonon transport equation (BTE) and first-principles calculations. The study employs a real-space finite displacement method to determine the second- and third-order interatomic force constants (IFCs), which are critical for solving the BTE iteratively. Our findings indicate that In2O3 and alpha-Ga2S3 exhibit relatively low thermal conductivities compared to other wide-bandgap semiconductors. At room temperature (300 K), the calculated isotropic thermal conductivity of cubic In2O3 is 16.2 Wm(-1) K-1. For monoclinic alpha-Ga2S3, the three principal components of thermal conductivity are 17.0, 20.7, and 15.2 W m(-1) K-1, depending on the crystallographic direction. This low thermal conductivity is primarily attributed to significant phonon scattering via three-phonon processes. Furthermore, we estimate the phonon mean free path (MFP) to be approximately 56 nm for In2O3 and between 198 and 231 nm for alpha-Ga2S3, varying with crystal orientation. These findings offer valuable insights into the thermal transport properties of In2O3 and alpha-Ga2S3, highlighting their potential for thermoelectric applications while delineating the constraints these properties impose on their use in electronic devices.