Calculation of the cross-plane thermal conductivity of a quantum cascade laser active region

The key problem in thermal modelling of a quantum cascade laser (QCL) is determining the thermal conductivity lambda of its active region. The parameter is highly anisotropic. In particular, the cross-plane value lambda(perpendicular to) is significantly reduced, which may be attributed to the presence of a large number of interfaces between epitaxial layers. In this work, two relatively simple models of phonon scattering at solid-solid boundary are used to calculate lambda(perpendicular to) for the terahertz QCL. The theoretical results are in good agreement with measurements.