Thermal conductivity of Si/SiGe superlattice films

We have evaluated the thermal conductivity of Si/SiGe superlattice films by theoretical analysis and experiment. In experiments, the ultrahigh vacuum chemical vapor deposition is employed to form the Si/Si0.71Ge0.29 and Si/Si0.8Ge0.2 superlattice films. The cross-plane thermal conductivities of these superlattice films are measured based on the 3ω method. In the theoretical analysis, the phonon transport in Si/Si1−xGex superlattice film is explored by solving the phonon Boltzmann transport equation. The dependence of the thermal conductivity of the Si/Si1−xGex superlattice films on the superlattice period, the ratio of layer thicknesses, and the interface roughness is of interest. The calculations show that when the layer thickness is on the order of one percentage of the mean free path or even thinner, the phonons encounter few intrinsic scatterings and consequently concentrate in the directions having high transmissivities. Nonlinear temperature distributions are observed near the interfaces, arising fr...