Molecular Dynamics Simulations of the Thermal Conductivity of Silicon-Germanium and Silicon-Germanium-Tin Alloys

Abstract

In this work, we investigate the thermal conductivity properties of ${\text{Si}}_{1-x}{\text{Ge}}_x$ and ${\text{Si}}_{0.8}{\text{Ge}}_0{\text{Sn}}_{2y}$ alloys. The equilibrium molecular dynamics (EMD) is employed to calculate the thermal conductivities of ${\text{Si}}_{1-x}{\text{Ge}}_x$ alloys when $x$ is different at temperatures ranging from 100 K to 1100 K. Then nonequilibrium molecular dynamics (NEMD) is used to study the relationships between $y$ and the thermal conductivities of ${\text{Si}}_{0.8}{\text{Ge}}_{0.2}{\text{Sn}}_{2y}$ alloys. In this paper, Ge atoms are randomly doped, and tin atoms are doped in three distributing ways: random doping, complete doping, and bridge doping. The results show that the thermal conductivities of ${\text{Si}}_{1-x}{\text{Ge}}_x$ alloys decrease first, then increase with the rise of $x$ , and reach the lowest value when $x$ changes from 0.4 to 0.5. No matter what the value of $x$ is, the thermal conductivities of ${\text{Si}}_{1-x}{\text{Ge}}_x$ alloys decrease with the increase of temperature. Thermal conductivities of ${\text{Si}}_{0.8}{\text{Ge}}_{0.2}$ alloys can be significantly inhibited by doping an appropriate number of Sn atoms. For the random doping model, thermal conductivities of ${\text{Si}}_{0.8}{\text{Ge}}_{0.2}{\text{Sn}}_y$ alloys approach the lowest level when $y$ is 0.10. Whether it is complete doping or bridge doping, thermal conductivities decrease with the increase of the number of doped layers. In addition, in the bridge doping model, both the number of Sn atoms in the [001] direction and the penetration distance of Sn atoms strongly influence thermal conductivities. The thermal conductivities of ${\text{Si}}_{0.8}{\text{Ge}}_{0.2}{\text{Sn}}_y$ alloys are positively associated with the number of Sn atoms in the [001] direction and the penetration distance of Sn atoms.