(Si)GeSn Nanostructures for Optoelectronic Device Applications

Inga Fischer, Institute for Semiconductor Engineering, University of Stuttgart
 

The application of Si and Ge to optoelectronics is limited due to their indirect bandgap and the concomitant low efficiency in optoelectronic applications. Alloying Ge with Sn can lead to a direct bandgap group-IV-material if the Sn content is high enough, however, the lattice mismatch of ~15% makes the growth of binary GeSn alloys challenging. The ternary alloy SiGeSn enables decoupling bandgap and lattice constant and is, therefore, an interesting candidate for optoelectronic device fabrication. The use of nanostructures composed of both GeSn and SiGeSn alloys could potentially facilitate the growth of Sn-rich, direct bandgap semiconductor layers and offer additional degrees of freedom in order to tune the bandgap as well as enhance optical properties as a result of carrier confinement in one or more directions. In this talk, the fabrication of GeSn and SiGeSn quantum dot and quantum well structures based on molecular beam epitaxy will be presented and their applications in optoelectronic devices such as photodetectors will be discussed. Furthermore, it will be discussed how combining group-IV-heterostructure devices with metallic nanostructures can modify optoelectronic properties towards possible applications in sensing.