Heavy hole effect on the thermoelectric properties of highly doped p-type lead telluride

摘要

We study theoretically the thermoelectric properties of heavily doped p-type PbTe in the temperature interval of 300 to 900 K. In our calculations, we use the three-band model of PbTe electron energy spectrum that takes into account the heavy-hole Σ-band. On the base of the Boltzmann kinetic equation, the full set of the relevant kinetic characteristics is calculated including the electrical and thermal conductivities, the Seebeck coefficient, and the thermoelectric figure-of-merit. The thermoelectric characteristics appear to be very sensitive to parameters of the heavy hole band. The best fit with experiment was obtained at m_(hh) = 5m_0 and E_(gΣ) = 0.5 eV. All calculated thermoelectric quantities then agree very well with the available experimental data. In particular, we were able to reproduce the significant increase of the figure-of-merit up to ZT ≈ 1.2 that was experimentally observed recently in heavily p-doped PbTe. Our results show that ZT maximum corresponds to the temperature wherein the light hole and heavy hole band edges coincide so that a prominent density-of-states singularity is formed in the valence band.