Substantial Phonon Nonequilibrium Near Nanoscale Hotspots in Ⅲ-Ⅴ Semiconductors

Abstract At nanoscale, as the heat carriers in semiconductors, phonons exert a significant impact on the performance of modern nanoelectronics. This paper reveals substantial phonon nonequilibrium near nanoscale hotspots in some III-V semiconductors based on the first-principle-based phonon Boltzmann transport equation (BTE), including wurtzite gallium nitride, aluminum nitride, and zinc-blende boron arsenide. We have illustrated that this unusually pronounced phonon nonequilibrium stems from two effects, i.e., the ballistic phonon transport and the selective phonon excitation. On one hand, the broad phonon mean free path (MFP) distributions of III-V semiconductors cause dominant ballistic phonon transport near nanoscale hotspots, where phonons with various MFPs are in strong nonequilibrium. On the other hand, the large electronegativity difference between constitute atoms leads to intense Fröhlich coupling between electrons and the longitudinal optical phonons, which indicates a strong selective phonon excitation and directly induces significant phonon nonequilibrium. These results provide an in-depth understanding of phonon dynamics in semiconductors and have a significant impact on improving the performance of advanced nanodevices.