MBE-based growth of Sn-rich quantum wells and dots at low Sn deposition rates

Alloying Ge with Sn is a possible route towards obtaining a direct bandgap material that can be integrated with Si technology for optoelectronic device applications. Low-dimensional structures such as GeSn quantum wells or islands are of particular interest, since those applications can benefit from quantum confinement effects. Here, we investigate the formation of Sn-rich quantum wells and islands formed by the deposition of few MLs of Sn on Ge and their overgrowth with Ge both based on a morphological characterization of the samples as well as photoluminescence measurements. We find that a low substrate temperature as well as a low deposition rate have an impact on the critical layer thickness at which the onset of Sn island formation can be observed and discuss the implications both for the samples grown and future research efforts.