Intrinsic electron mobility and lattice thermal conductivity of β-Si3N4 from first-principles

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Silicon nitride based materials have emerged as the promising candidates for high-power electronics and next-generation gate dielectrics. Herein, the crucial characteristics of electron mobility and lattice thermal conductivity of β-Si3N4 are investigated from first-principles. The predicted electron mobility and averaged lattice thermal conductivity is 228.4 cm2/Vs and 325.06 W/m·K at 300 K, which demonstrates a good agreement with literature data. The electron mobility exhibits strong temperature-dependence at a low carrier concentration where the polar-optical phonon scattering dominates. For the heavy doping case, the ionized impurity scattering becomes dominant. A well-trained momentum tensor potential (MTP) with an accuracy comparable to density functional theory shows advantages in predicting thermal transport properties over a large-scale system containing thousands of atoms. The relaxation lifetimes for heat-carrying acoustic phonons are over tens of picoseconds which can explain the high thermal conductivity of β-Si3N4, but the nanoscale grain size crucially limits the thermal transport properties.