Ballistic heat transport in thin oxide layers

In this project, the thermal conductivity in the transition region from diffusive to ballistic thermal transport will be investigated experimentally. The aim is to unambiguously identify the regime of ballistic phonon transport. For this purpose, the thickness of semiconducting oxide layers will be reduced from several 100 nm down to 5-10 nm. As a model system with great application potential, e.g. in power electronics, beta-gallium oxide is grown as epitaxial layers and investigated in comparison to exfoliated nearly defect-free single crystalline layers. Based on our promising preliminary work on electrical and thermal transport on bulk single crystalline material and exfoliated films, epitaxial films of beta-gallium oxide with nanometer-scale film thicknesses will be fabricated. Phonon scattering responsible for thermal transport will be studied as a function of temperature, film thickness, and doping.