Influence of interfacial selectivity on heat transport at multi-interfaces in AlGaN/GaN FinFET

With continued transistor scaling and rising power densities, thermal management has become a critical challenge in modern electronic devices. In particular, hotspot formation and interfacial thermal resistance are two major factors limiting efficient heat dissipation. While previous studies have examined hotspot-induced nonequilibrium effects and interfacial phonon scattering separately, the coupling between localized hotspots and interfacial transport remains insufficiently explored. This study focuses on AlGaN/GaN FinFETs and their internal interfaces, employing the multitemperature model (MTM) and the Boltzmann transport equation (BTE) to investigate nonequilibrium and ballistic thermal transport mechanisms. A novel specific thermal resistance decomposition method is developed to quantitatively separate intrinsic, nonequilibrium, and ballistic contributions to specific thermal resistance, enabling a more mechanistic understanding of phonon transport behavior. Our results reveal that the selective excitation of hotspots and the interfacial selectivity are key contributors to nonequilibrium and ballistic effects. Specifically, while the Au/GaN interface preferentially transmits low-frequency phonons, hotspots predominantly excite high-frequency phonons. This spectral mismatch suppresses interfacial heat transfer, and due to interfacial selectivity, the influence of hotspots seldom extends across the interface. Notably, at locations near the interface, the influence of the hotspot is significantly weakened, both in terms of nonequilibrium transport and ballistic transport, highlighting the critical role of interfacial selectivity in hotspot thermal transport. Device-level simulations further demonstrate that ballistic transport impedes heat dissipation near the hotspot, exacerbating local nonequilibrium and elevating peak temperatures. This work systematically analyzes the interplay between selective excitation and interfacial selectivity in the AlGaN/GaN FinFET, and introduce a novel decomposition methodology to isolate ballistic and nonequilibrium effects in specific thermal resistance. These insights offer a new direction for understanding and regulating thermal transport in nanoscale FETs.