Fabrication and properties of optoelectronic SiGeSn alloys integrated on silicon substrates

Attempts to decouple band gap from strain-engineering in group IV materials motivated a significant effort to develop ternary SiGeSn alloys. These grow either directly on Si (100) or on GeSn- and Ge-buffered Si substrates, remain stable at temperatures beyond 800°C (depending on composition), and display intriguing electronic and transport properties. In particular, the complete decoupling of electronic structure and lattice constant was demonstrated in a specific family of SiGeSn alloys lattice-matched to Ge [1] and transport measurements in n- and p-type analogs reveal mobilities comparable to those in elemental Ge. Combined with novel CVD approaches to the growth of binary GeSn alloys [2] as well as superior quality Ge films on Si substrates [3], these materials represent an entire new class of IR semiconductors with the potential to revolutionize the field of group-IV materials. The purpose of this paper is to review the preparation and properties of SiGeSn alloys and discuss their potential for photonic applications. The two-dimensional compositional space of this system as well as the many possible lattice matched and un-matched combinations of ternary, binary, and elemental group-IV semiconductors provide unprecedented flexibility to further develop and optimize the basic properties of these materials for optoelectronic, thermoelectricity and potentially photovoltaics.