We examine the temperature dependence of silicon (Si) thermal conductivity as a function of doping level across a range of p- and n-type concentrations varying from 1014 cm-3 to 1019 cm-3. Interestingly, there is still a debate on the reason why thermal conductivity decays at high doping: usual analytical work tends to suggest that the reason is impurity scattering of phonons while more-recent ab-initio work demonstrates that electron scattering of phonons [1] could surpass impurity scattering. Most high-doping experimental data were obtained at room temperature, so analysing the temperature dependence of this effect could help in settling the discussion. We have systematically characterized planar Si substrates, covered with a 200 nm-thick silicon dioxide layer, by using the 3ω method [2] over temperatures ranging from 80 K to 303 K. Thermal conductivity of the Si samples is determined by comparing experimental results with a semi-analytical model [3]. The obtained lattice thermal conductivity values are compared to analytical models based on the Boltzmann transport equation and other published experimental results, with an emphasis on recent DFT data. In particular, we provide an expression of the critical doping at which thermal conductivity starts to reduce, as a function of temperature. These results help understanding how to resolve the controversy related to the key mechanism of the high-temperature thermal-conductivity decay.
[1] B. Liao et al., Phys. Rev. Lett. 114, 115901 (2015)
[2] D. G. Cahill, Rev. Sci. Instrum. 61, 802 (1990)
[3] T. Borca-Tasciuc, A. R. Kumar and G. Chen, Rev. Sci. Instrum. 72, 2139 (2001)
We acknowledge the support of project EFICACE (ANR-20-CE09-0024).