Simulation of interfacial phonon transport in Si-Ge heterostructures using an atomistic Green's function method

An atomistic Greens function method is developed to simulate phonon transport across a strained germanium (or silicon) thin film between two semi-infinite silicon (or germanium) contacts. A plane-wave formulation is employed to handle the translational symmetry in directions parallel to the interfaces. The phonon transmission function and thermal conductance across the thin film are evaluated for various atomic configurations. The contributions from lattice straining and material heterogeneity are evaluated separately, and their relative magnitudes are characterized. The dependence of thermal conductance on film thickness is also calculated, verifying that the thermal conductance reaches an asymptotic value for very thick films. The thermal boundary resistance of a single Si/Ge interface is computed and agrees well with analytical model predictions. Multiple-interface effects on thermal resistance are investigated, and the results indicate that the first few interfaces have the most significant effect on the overall thermal resistance.