2D Materials Enhance Thermal Conductance at van der Waals Interfaces of β-Ga ₂ O ₃

Wide bandgap (WBG) semiconductors have enabled the advancement of next-generation radio frequency, opto-, and power electronics. Among them, β-Ga 2 O 3 has attracted enormous interest because it can withstand higher voltages with higher efficiencies and can be fabricated using relatively low-cost melt-growth techniques. However, it suffers from lower thermal conductivity than nitrides or carbides, which could lead to device performance degradation. One way to ensure adequate thermal management is to place β-Ga 2 O 3 on a highly thermally conductive substrate. However, the low thermal boundary conductance (TBC) at the interface limits heat flow to the substrate, necessitating ways to improve TBC. We investigate the possibility of improving the TBC of van der Waals bonded β-Ga 2 O 3 /3D interfaces using 2D material interlayers. Our model employs phonon dispersions calculated from first-principles while phonon transmission rates across β-Ga 2 O 3 /2D interfaces are determined from perturbation theory. To compare TBC with and without the 2D layer, we also model TBC across β-Ga 2 O 3 /3D interfaces with our new implementation of the van der Waals-based AMM model that utilizes the same first-principles phonon dispersions. Our study shows that the large overlap between the phonon density of states of β-Ga 2 O 3 and that of 2D materials can be utilized to enhance TBC of β-Ga 2 O 3 /3D interfaces significantly. In addition, we show that TBC can be enhanced further by increasing the number of layers of the 2D materials because additional layers boost the number of phonon modes available for heat transfer. However, if the surface roughness at the interface is very steep, as captured by surface roughness slope, TBC drops due to partial delamination of the 2D material, which reduces the effective interfacial coupling. Therefore, our study provides valuable insights into optimizing TBC of β-Ga 2 O 3 /3D interfaces through 2D materials interlayers and interface engineering, which will contribute to improving thermal management in electronic devices made of β-Ga 2 O 3 .