If the capability to control photons and electrons in crystals has brought to an astonishing level of knowledge as well as to extraordinary technological achievements, the manipulation of phonons is still quite unexplored, despite it holds the promise of a quantum-mechanical control of heat transport. The quantum-mechanical behavior of phonons may also enable the realization of coherent phonon transport via phonon engineering. Nanostructures, such as semiconducting nanowires (NWs), are an ideal platform for phonon engineering, since they offer the possibility to modify to a large extent the phononic properties by enabling the formation of different kinds of superlattices and heterostructures.
Indeed, III-V NWs display a unique property, which is the existence of polytypism, namely the possibility to grow in zincblende (ZB) or wurtzite (WZ) crystal phase. This has widened the potential applications of technologically relevant III-V compounds such as GaAs, InP, and GaP, for which WZ does not exist in bulk form. The controlled switching between different crystal phases during the NW growth opened the way to crystal phase engineering and to the formation of novel types of superlattices. I will show how the phononic properties can be designed à la carte by tuning the superlattice period in NWs, as demonstrated by Raman spectroscopy, and discuss the future developments in thermal transport.
In the second part of the talk, I will introduce the open challenges in Nano-photonics. I will present a new approach for embedding site-controlled quantum dots in III-V NWs. The pursued route will involve post-growth hydrogen incorporation, thus allowing to achieve different NW properties on demand with no need to change and re-optimize NW growth conditions. Dots-in-NWs with high brightness and high light extraction efficiency can be the solid-state building blocks of novel photonic crystals and photonic circuits, and open new paths in quantum computation and communication.
Hosted by Riccardo Rurali, Researcher at the Theory and Simulation Group