Cross-plane thermal conductivity of GaN/AlN superlattices

Heterostructures consisting of alternating GaN/AlN epitaxial layers represent the building blocks of state-of-the-art devices employed for active cooling and energy-saving lightning. Insights into the heat conduction of these structures are essential in the perspective of improving the heat management for prospective applications. Here, the cross-plane (perpendicular to the sample's surface) thermal conductivity of GaN/AlN superlattices as a function of the layers' thickness is established by employing the 3ω -method. Moreover, the role of interdiffusion at the interfaces in the phonon scattering is taken into account in the modeling and data treatment. It is found that the cross-plane thermal conductivity of the epitaxial heterostructures can be driven to values as low as 5.9 W/(m·K) comparable with those reported for amorphous films, thus opening wide perspectives for optimized heat management in III-nitride-based epitaxial multilayers. This work was supported by the European Commission's Horizon 2020 Research and Innovation Program [Grant No. 645776 (ALMA)] and by the Austrian Science Fund (FWF) (Project Nos. P31423 and P26830). For the purpose of open access, the author has applied a CC BY public copyright license to any author accepted manuscript version arising from this submission. The authors thank Werner Ginzinger for preparing the specimens for the TEM experiments and for carrying out the related measurements, Heiko Groiss and Jesús Carrete for fruitful discussions, and Albin Schwarz for preparing the contact structures for the 3ω measurements.