Modeling and Analysis of Strain Effects on Thermoelectric Figure of Merit in Si/Ge Nanocomposites

Abstract

In this chapter, strain effect on the thermoelectric figure of merit is investigated in n-type Si/Ge nanocomposite materials. Strain effect on phonon thermal conductivity in the nanocomposites is computed through a model combining the strain-dependent lattice dynamics and the ballistic phonon BTE. The Seebeck coefficient and electrical conductivity of the Si/Ge nanocomposites are calculated by an analytical model derived from the Boltzmann transport equation (BTE) under the relaxation-time approximation. The effect of strain is incorporated into the BTE through strain-induced energy shift and effective mass variation calculated from the deformation potential theory and a degenerate k ⋅ p method at the zone-boundary X point. Electronic thermal conductivity is computed from electrical conductivity by using the Wiedemann–Franz law. Various strains are applied in the transverse plane of the Si/Ge nanocomposites. Thermoelectric properties including thermal conductivity, electrical conductivity, Seebeck coefficient, and dimensionless figure of merit are computed for Si/Ge nanocomposites under these strain conditions.KeywordsSeebeck CoefficientEffective Thermal ConductivityStrain EffectBoltzmann Transport EquationControl AngleThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.