A unified wave-particle treatment for phonon transport in superlattices

The phonon thermal conductivity of semiconductor superlattices is calculated with the use of a unified wave-particle model. This model points out that phonons in most semiconductor superlattices of interest are neither pure superlattice modes nor pure bulk modes, but in the mixing-mode regime. The phonons are rationally divided into bulk-like and superlattice-like modes according to the mean free path and the minimum number of periods required to form superlattice bands. The theoretic results are used to explain the thermal conductivity data in both the cross-plane and inplane directions of GaAs/AlAs superlattices.