Thermal conductivity of ultra-wide bandgap thin layers – High Al-content AlGaN and β-Ga2O3

Transient thermoreflectance (TTR) technique is employed to study the thermal conductivity of β-Ga2O3 and high Al-content AlxGa1-xN semiconductors, which are very promising materials for high-power device applications. The experimental data are analyzed with the Callaway's model taking into account all relevant phonon scattering processes. Our results show that out-of-plane thermal conductivity of high Al-content AlxGa1-xN and (−201) β-Ga2O3 is of the same order of magnitude and approximately one order lower than that of GaN or AlN. The low thermal conductivity is attributed to the dominant phonon-alloy scattering in AlxGa1-xN and to the strong Umklapp phonon-phonon scattering in β-Ga2O3. It is also found that the phonon-boundary scattering is essential in thin β-Ga2O3 and AlxGa1-xN layers even at high temperatures and the thermal conductivity strongly deviates from the common 1/T temperature dependence. •New experimental data for thermal conductivity of (−201) β-Ga2O3 and high Al-content AlGaN layers measured by transient thermoreflectance (TTR) technique.•Umklapp phonon-phonon scattering limited thermal conductivity in (−201) β-Ga2O3.•Sn doping dependent thermal conductivity of (−201) β-Ga2O3.•Phonon-alloy disorder determined thermal conductivity in high Al-content AlGaN.