Apparent interface conductance of Si (black squares), Si0.99Ge0.01 (red circles), Si0.2Ge0.8 (green circles) and Ge (orange squares) along with the predictions of a ballistic/diffusive model (solid lines). The value of GA for Si shown here differs from the value reported in Fig. 1 because the data in Fig. 1 is for a sample that did not have the native oxide removed before Al deposition. The low thermal diffusivity of Si0.99Ge0.01 and Si0.2Ge0.8 results in a large interfacial nonequilibrium thermal resistance that effects the value of GA at low f, resulting in a lower value of GA than is observed for Si or Ge.