  This paper presents a semiclassical model for the anisotropic thermal
transport in III-V semiconductor superlattices (SLs). An effective interface
rms roughness is the only adjustable parameter. Thermal transport inside a
layer is described by the Boltzmann transport equation in the relaxation time
approximation and is affected by the relevant scattering mechanisms
(three-phonon, mass-difference, and dopant and electron scattering of phonons),
as well as by diffuse scattering from the interfaces captured via an effective
interface scattering rate. The in-plane thermal conductivity is obtained from
the layer conductivities connected in parallel. The cross-plane thermal
conductivity is calculated from the layer thermal conductivities in series with
one another and with thermal boundary resistances (TBRs) associated with each
interface; the TBRs dominate cross-plane transport. The TBR of each interface
is calculated from the transmission coefficient obtained by interpolating
between the acoustic mismatch model (AMM) and the diffuse mismatch model (DMM),
where the weight of the AMM transmission coefficient is the same
wavelength-dependent specularity parameter related to the effective interface
rms roughness that is commonly used to describe diffuse interface scattering.
The model is applied to multiple III-arsenide superlattices, and the results
are in very good agreement with experimental findings. The method is both
simple and accurate, easy to implement, and applicable to complicated SL
systems, such as the active regions of quantum cascade lasers. It is also valid
for other SL material systems with high-quality interfaces and predominantly
incoherent phonon transport.
