Significantly reduced thermal conductivity in β-(Al0.1Ga0.9)2O3/Ga2O3 superlattices.

β-Ga₂O₃ has emerged as a promising candidate for electronic device applications because of its ultrawide bandgap, high breakdown electric field, and large-area affordable substrates grown from the melt. However, its thermal conductivity is at least one order of magnitude lower than that of other wide bandgap semiconductors such as SiC and GaN. Thermal dissipation in electronics made from β-Ga₂O₃ will be the bottleneck for real-world applications, especially for high power and high frequency devices. Similar to AlGaN/GaN interfaces, β-(Al_xGa_1−x)₂O₃/Ga₂O₃ heterogeneous structures have been used to form a high mobility two-dimensional electron gas where joule heating is localized. The thermal properties of β-(Al_xGa_1−x)₂O₃/Ga₂O₃ are the key for heat dissipation in these devices, while they have not been studied before. This work reports the temperature dependent thermal conductivity of β-(Al_0.1Ga_0.9)₂O₃/Ga₂O₃ superlattices from 80 K to 480 K. Its thermal conductivity is significantly reduced (5.7 times reduction) at room temperature compared to that of bulk Ga₂O₃. Additionally, the thermal conductivity of bulk Ga₂O₃ with (010) orientation is measured and found to be consistent with literature values regardless of Sn doping. We discuss the phonon scattering mechanism in these structures by calculating their inverse thermal diffusivity. By comparing the estimated thermal boundary conductance (TBC) of β-(Al_0.1Ga_0.9)₂O₃/Ga₂O₃ interfaces and Ga₂O₃ maximum TBC, we reveal that some phonons in the superlattices transmit through several interfaces before scattering with other phonons or structural imperfections. This study is not only important for Ga₂O₃ electronics applications, especially for high power and high frequency applications, but also for the fundamental thermal science of phonon transport across interfaces and in superlattices. [ABSTRACT FROM AUTHOR]