Direct-gap photoluminescence with tunable emission wavelength in Ge1-ySny alloys on silicon

Direct-gap photoluminescence has been observed at room temperature in Ge1-ySny alloys grown on (001) Si substrates. The emission wavelength is tunable over a 90 meV (200 nm) range by increasing the Sn concentration from y=0 to y=0.03. A weaker feature at lower energy is assigned to the indirect gap transitions, and the separation between the direct and indirect emission peaks is found to decrease as a function of y, as expected for these alloys. These results suggest that Ge1-ySny alloys represent an attractive alternative to Ge for the fabrication of laser devices on Si. (C) 2010 American Institute of Physics. [doi:10.1063/1.3521391]