Ultrahigh thermal conductance between III-nitride semiconductor and diamond via interfacial atomic reordering

Thermal management stands as a critical bottleneck in advancing next-generation high-power electronics implemented on III-nitride semiconductors. As the best thermal conductor, diamond offers unprecedented cooling potential via heterogeneous integration. In practice, however, the total thermal resistance remains unacceptably high due to disordered interfaces, which also obscures understanding of fundamental phonon transport mechanisms. Here, by employing a plasma-induced interfacial atomic reordering strategy, we achieve a sharp and ordered interface between aluminum nitride (AlN) and single-crystalline diamond, with substitutional nitrogen atoms (N_C). We demonstrate a record-high interfacial thermal conductance of ~880 MW·m-2K-1, approaching the maximum transmission limit (MTL). Atomically-resolved electron energy-loss spectroscopy and machine-learning molecular dynamics reveal that the low-energy phonon spectrum in diamond aligns well with acoustic phonons in AlN, dominating heat flow across the interface. Additionally, interfacial modes arising from N_C at the interface offer additional phonon pathways. Our findings highlight interfacial atomic reordering as a promising avenue for passively cooling future electronics.