Photoluminescence from heavily doped GeSn:P materials grown on Si(100)

Photoluminescence has been observed at room temperature in phosphorus-dopedGe1−ySny/Si(100) alloys containing carrier densities in the 1-6 × 1019 cm−3 range. The emission intensity is one order of magnitude stronger than observed in similar undoped films, and the enhancement is consistent with theoretical predictions for doped-Ge like materials. The ratio Idir/Iind of direct over indirect gap emission is found to increase for high-Sn concentrations as a result of the reduced Γ-L valley separation in Ge1−ySny alloys. These results confirm that alloying with Sn is a viable alternative to tensile strain as a tool to enhance direct-gap emission in Ge-like semiconductors.