Ab Initio Investigation of Thermal Conductivity of Ge_xSn_(1-x)O₂

GeO₂ is an emerging ultra-wide band gap (UWBG) semiconductor that has demonstrated excellent potential in the application of power electronic devices. Alloying GeO₂ with SnO₂, a well-established UWBG material, offers tunability of material properties for optimized device performance. Recent studies demonstrated excellent electronic transport properties of Ge_xSn_1-xO₂ alloys, rendering them as strong candidates for next-generation power electronics. However, thermal management remains a key challenge, as thermal conductivity directly affects device performance and reliability by governing heat dissipation and preventing degradation.
In this work, we employ first-principles method to study the lattice thermal conductivity of the Ge_xSn_(1-x)O₂ alloy. We use density functional theory (DFT) to study the electronic structure and density functional perturbation theory (DFPT) for phonon properties. We study the alloy using the virtual crystal approximation taking into account the mass disorder caused by alloying. By solving the Boltzmann transport equations (BTE) with the almaBTE software, we calculate the phonon-limited thermal conductivity of both the end compounds and the alloy system.
Our characterization shows that alloy disorder reduces the thermal conductivity of the material by approximately a factor of five. Despite this reduction, the alloy's thermal conductivity remains comparable to other prominent UWBG power electronic materials such as Ga₂O₃. We further explore the temperature-, composition-, and phonon-mean-free-path- dependent behavior of thermal conductivity, offering practical guidance for designing thermally efficient devices. This comprehensive study provides crucial insights into the factors limiting thermal transport in Ge_xSn_(1-x)O₂ and highlights specific pathways for improving material performance in practical applications.
This material is based upon work supported by the National Science Foundation under grant no. 2328701 and is supported in part by funds from federal agency and industry partners as specified in the Future of Semiconductors (FuSe) program. It used resources of the National Energy Research Scientific Computing (NERSC) Center, a DOE Office of Science User Facility supported under Contract No. DE-AC02–05CH11231.