Prof. Zoran Ikonic from University of Leeds visited SCL and presented a seminar:

"Electronic structure and optoelectronic applications of SiGeSn alloys"

Abstract:

SiGeSn alloys have emerged as a new class of semiconductor alloys, offering a direct band gap in the group IV system and being at the same time fully compatible with Si CMOS processing. They enable independent variation of band gaps and lattice constant, and can be used in both lattice-matched and strained layer structures. With the possibility of emission and absorption in the near- and mid-IR range, there is prospect of applications for interband and quantum cascade lasers, photodetectors, electro-absorption and electro-optic modulators, etc. The direct gap – most important for emission – may be brought about by alloy composition alone or combined with strain. In the context of group IV optoelectronics, indirect gap SiGeSn alloys can also serve as barrier layers in structures based on GeSn or Ge quantum wells, or for the virtual substrate / stressor purposes. Reliable growth of high-quality SiGeSn structures has proved quite challenging. With a very small equilibrium solubility of Sn, and large lattice mismatch between Sn and Ge/Si, the SiGeSn system is metastable and cannot be readily produced in bulk form, and heterostructures may suffer from strain relaxation. The recent successes in this field pave the way towards materials that combine the optical properties of III-Vs and silicon’s low cost manufacturability. The present status of theoretical understanding and experimental achievements in the development of SiGeSn material for optoelectronic applications is reviewed.