2D materials Enhance Thermal Boundary Conductance at van der Waals Interfaces of β-Ga₂O₃

Wide bandgap (WBG) semiconductors have enabled the advancement of next-generation radiofrequency, opto-, and power electronics. Among them, β-Ga₂O₃ has emerged as a leader because it can withstand higher voltages with higher efficiencies and can be fabricated using relatively cheap melt-growth techniques. However, it suffers from limited thermal conductivity which could lead to Joule heating and performance degradation. Therefore, to ensure efficiency and reliability of devices with β-Ga₂O₃ channels, effective methods of heat dissipation are needed. In this study, we show that high TBC at β-Ga₂O₃/2D interfaces can be used to improve β-Ga₂O₃/substrate TBC by adding interlayers of 2D materials at the interface. β-Ga₂O₃ has large vibrational density of states in the low-frequency range where it overlaps well with the flexural phonons of 2D materials leading to a high TBC across β-Ga₂O₃/2D interfaces, unlike other WBG materials such as diamond. Layers of hBN show the highest TBC of 19.9 MW/m²K for combined 3D-2D-3D interfaces of β-Ga₂O₃/hBN/Ti at room temperature. We show that TBC relates to the overlap of vibrational densities of states (DOS) and that it can be further increased by more than 30% when the number of 2D layers is increased from 1 to 12 due to an increase in the number of flexural phonon branches, which increases the DOS overlap. Our study provides important information and will contribute to the realization of efficient thermal management of thin-film wafer-bonded β-Ga₂O₃ electronic devices.