First-principles study of enhanced thermal conductivity in ordered AlGaO₃alloys

Monoclinic gallium oxide (Ga₂O₃) has promising applications in high-power and high-frequency electronics due to its wide band gap. However, practical device applications are hampered by its low thermal conductivity. To improve the thermal properties of Ga₂O₃ devices, we propose to alloy Ga₂O₃ with Al₂O₃, forming a low-energy ordered structure at the 50% concentration [1]. We investigate the lattice thermal conductivity of monoclinic Ga₂O₃ and of the ordered AlGaO₃ alloy using the phonon Boltzmann transport equation, with the harmonic and third-order anharmonic force constants calculated from density functional theory. We find that the thermal conductivity of AlGaO₃ is raised by more than 70% compared to Ga₂O₃. The enhancement is ascribed to (1) increased group velocities and (2) reduced anharmonic scattering rates due to the reduced weighted phase space. The findings offer an avenue towards improved heat dissipation from Ga₂O₃ devices.
The work was supported by the GAME MURI of the Air Force Office of Scientific Research.

[1] H. Peelaers et al., Appl. Phys. Lett. 112, 242101 (2018).