We report on the contribution of optical phonon decay into acoustic phonon to the thermal
conductivity [k (T)] of semiconductors. We have considered this mechanism as an acoustic
phonon generation rate within the full modified Callaway theory to accurately describe
experimental data of k (T) for Ge as a function of isotopic composition. The proposed model
requires only one adjustable parameter for each mode. Our approach to describe k (T) in
semiconductors is found to provide much better agreement with the experimental results …