Silicon is ordinarily transparent to infrared (IR) light with wavelengths longer than 1.00 nm, limiting its applicability to technologies where infrared response is important. Recent work has shown that by supersaturating silicon with an impurity (e.g., sulfur or gold), strong broadband sub band gap absorption is observed, with device response below the silicon band gap.   Other work has shown that incorporating high concentrations of Sn into Ge leads to Ge becoming a direct band gap material, with a tunable band gap.  Recent results have shown that GeSn alloys exhibit short range order, which could lead to tunable optoelectronic properties with the same alloy composition.  Fundamental scientific work is needed to understand the structural and optoelectronic properties of material systems like these and the role and ability of laser processing to fabricate such materials.  Applied research is needed to define device architectures and to fabricate and measure the resulting devices. The overarching goal will be comparison of the material to conventional IR materials such as InGaAs. A low-cost CMOS-compatible IR optoelectronic material would be a significant technological breakthrough.

References

Mailoa et al:  Nature Communications 5: 3011 (2014)

Warrender,  Appl Phys Rev 3: 031104 (2016)

Michel et al., Nature Photonics 4, 527 (2010) 

S. Wirths et al., Nature Photonics 9, 88 (2015)

Bob B, et al: Journal of Applied Physics 107: 123506, 2010

Tabbal M, et al: Journal of Vacuum Science and Technology B 25: 1847, 2007