Rydberg excitons in Cu2O microcrystals grown on a silicon platform

Cuprous oxide (Cu2O) is a semiconductor with large exciton binding energy and significant technological importance in applications such as photovoltaics and solar water splitting. It is also a superior material system for quantum optics that enabled the observation of intriguing phenomena, such as Rydberg excitons as solid-state analogue to highly-excited atomic states. Previous experiments related to excitonic properties focused on natural bulk crystals due to major difficulties in growing high-quality synthetic samples. Here, the growth of Cu2O microcrystals with excellent optical material quality and very low point defect levels is presented. A scalable thermal oxidation process is used that is ideally suited for integration on silicon, demonstrated by on-chip waveguide-coupled Cu2O microcrystals. Moreover, Rydberg excitons in site-controlled Cu2O microstructures are shown, relevant for applications in quantum photonics. This work paves the way for the wide-spread use of Cu2O in optoelectronics and for the development of novel device technologies.