Non-equivalent thermal conductance at isomorphic interfaces

Atomically precise interfaces in semiconductors are essential for optimal electronic, thermal, and optical properties in nanodevices. As miniaturization advances, the decreasing spacing of interfaces amplifies their role in phonon-mediated properties, especially thermal transport. While interfacial thermal conductance (ITC) has been extensively studied at interfaces with and without lattice discontinuities, research focusing on non-equivalent ITC at isomorphic interfaces, where the lattice symmetry is identical but atomic arrangements differ, remains limited. Here, we investigate non-equivalent ITCs at AlN/GaN and GaN/AlN interfaces using density functional theory (DFT)-based machine-learning molecular-dynamics (MLMD) simulations. Though both interfaces share the same lattice symmetry, the atomic arrangements differ: in the AlN/GaN interface, each N atom bonds with one Al and three Ga atoms, while in the GaN/AlN interface, each N atom bonds to one Ga and three Al atoms. The calculated ITCs exhibit a 10% difference, attributed to distinct interface phonons localized at interfacial N atoms, as demonstrated by spectral-heat-current analysis. We propose a strategy of atomic mass engineering to modulate the ITC non-equivalence. Moderate intermixing is also considered to check the effects. The results highlight the significant role of interface phonons in ITC and provide insights into the thermal management of nanodevices.