CeNS Colloquium

Prof. Wolfgang Hansen
Institut für Angewandte Physik, Universität Hamburg

We apply a novel droplet etching method to prepare self-assembled semiconductor nanopillars that bridge an air gap between layers in a semiconductor heterostructure grown by molecular beam epitaxy. The nanopillars have a diameter of about 100 nm, a length of typically 5-10 nm, and are perfectly lattice matched to the layers of the heterostructure. In this talk, I will report about studies of the vertical thermal conductance in the structure. The nanopillars form ballistic point contacts between three-dimensional phonon reservoirs. Indeed, our experimental findings are well described with a simple model assuming ballistic phonon transport through point contacts up to room temperature. Applications of the droplet etching method in semiconductor epitaxy such as thermoelectric devices, current injectors, and quantum-dot devices will be discussed.