Molecular dynamics simulations of oblique phonon scattering at semiconductor interfaces

Equilibrium molecular dynamics simulations are used to determine the transmission probability of oblique phonons scattering on flat and rough surfaces. The transmission is determined from the total energy change of the materials comprising the interface. We consider semiconductor films of silicon (Si) and germanium (Ge) as interfacing materials. A symmetric sawtooth (triangular) structure of varying height (similar to that analyzed in Appl. Phys. Lett., 93(8), 2008) is used to introduce surface roughness. We have found that the transmission is a strong function of the phonon incident angle, frequency, mass ratio of the comprising semiconductors and roughness height. An interesting behavior in the transmission probability is observed with the introduction of controlled surface roughness. Low frequency phonons can have transmission values higher than those predicted in the acoustic limit. Conversely, they decrease significantly for high frequency phonons. Maximum and minimum values in the transmission probability are found for surface roughness of 4.34 nm height.