Ab initio thermal conductivity of Ge$_x$Sn$_{1-x}$O$_2$ alloys

Abstract: Rutile GeO2 is an emerging ultra-wide band gap semiconductor (UWBG) that has demonstrated excellent potential for applications in power electronic devices. Alloys of rutile SnO2, a well-established UWBG semiconducting oxide, with GeO2 are promising for tuning the material properties for applications. The thermal conductivity, in particular, is a key property which is significantly impacted by alloy disorder, but which is also essential in assessing the operation and degradation of materials in high-power electronic applications. Here, we present first-principles calculations of the thermal conductivity of rutile GeO2, SnO2, and their alloys, and quantify the effects of scattering by alloy disorder, temperature, and isotope mass distribution. We show that the relatively high thermal conductivity of the binary compounds is reduced by alloying, grain boundaries, and isotope disorder. However, we also find that the room-temperature thermal conductivity of the alloys is still comparable to or surpasses the values for beta-Ga2O3, an established UWBG semiconducting oxide. Our findings provide a roadmap for the codesign of the thermal properties of rutile GexSn1-xO2 alloys for electronic device applications.