Mechanism of thermal conductivity suppression in doped silicon studied with nonequilibrium molecular dynamics

Abstract

We examined the underlying mechanisms for thermal conductivity suppression in crystalline silicon by substitutional doping with different elements ($X$ $=$ boron, aluminum, phosphorus, and arsenic). In particular, the relative effects of doping-induced mass disorder, bond disorder, and lattice strain were assessed using nonequilibrium molecular dynamics simulations. Stillinger--Weber potential parameters for Si-$X$ interatomic interactions were optimized by fitting to relevant atomic forces from first-principles calculations. We first calculated the thermal conductivity variation of B-doped Si as a function of dopant concentration; the result shows excellent agreement with existing experimental data, indicating the reliability of our force-field-based simulations. At the dopant concentration of about 5 \ifmmode\times\else\texttimes\fi{} 10${}^{20}$ cm${}^{\ensuremath{-}3}$, the Si thermal conductivity value is predicted to be reduced from 137 W/mK at 300 K in undoped Si to 18/39/57/78 W/mK in As/B/P/Al-doped Si. Our study demonstrates that the mass disorder effect is primarily responsible for the thermal conductivity suppression in the As- and B-doped cases, whereas the bond disorder contribution is found to be more important than the mass disorder contribution in the Al- and P-doped cases; for all these systems, the lattice strain effect turns out to play a minor role in the reduction of lattice thermal conductivity.