Thermal conductivity of Si/Ge superlattices: A realistic model with a diatomic unit cell

This paper considers the effects of a realistic description of phonons in d iamondlike semiconductors and their conversion on the abrupt heterointerfac es on the thermal conductivity of the superlattice (SL). Due to the much la rger mass of Ge atoms in comparison to Si, the most probable acoustic phono ns in Si layers at room temperature have no counterpart in Ge. in simplifie d models where Si and Ge are simulated by monatomic crystals with fitted pa rameters, this leads to the highly efficient trapping of high-energy acoust ic phonons in Si layers and drastic reduction of the SL thermal conductivit y. The proposed approach incorporates the optical branches and the effectiv e conversion of the phonons at interfaces extends the temperature range for which the model is valid and thereby leads to corrections to predicted the rmal conductivity.