Ab initio study of enhanced thermal conductivity in ordered AlGaO3 alloys

Abstract

We compute the lattice thermal conductivity of monoclinic β-Ga2O3 and the ordered AlGaO3 alloy from the phonon Boltzmann transport equation, with the harmonic and third-order anharmonic force constants calculated from density functional theory. The calculated thermal conductivity of β-Ga2O3 is consistent with experiment. We demonstrate that the lowest-energy structure of an Al0.5Ga0.5 alloy, which is ordered, has a thermal conductivity that is raised by more than 70% compared to β-Ga2O3. We attribute the enhancement to (1) increased group velocities and (2) reduced anharmonic scattering rates due to the reduced weighted phase space. The findings offer an avenue toward improved heat dissipation from Ga2O3 devices. The authors acknowledge Shengying Yue, Jingjing Shi, Samuel Graham, and Yuewei Zhang for fruitful discussions. This work was supported by the GAME MURI of the Air Force Office of Scientific Research (No. FA9550-18-1-0479). Computing resources were provided by the Center for Scientific Computing supported by the California NanoSystems Institute and the Materials Research Science and Engineering Center (MRSEC) at UC Santa Barbara through the National Science Foundation (NSF) (Nos. DMR-1720256 and CNS-1725797) and by the Extreme Science and Engineering Discovery Environment (XSEDE), which was supported by NSF Grant No. ACI-1548562.