Light from germanium tin heterostructures on silicon

GeSn LED's with Sn contents up to 4% exhibit light emission from the direct band transition although GeSn of low Sn contents is an indirect semiconductor.. The emission wavelength is red shifted compared to Ge. The redshift of the direct band transition is confirmed by different optical characterization techniques as photoluminescence, electroluminescence, photodetection and reflectivity. The photon emission energy decreases from 0.81 eV to 0.65 eV for compressively strained GeSn of 0% to 4% Sn content. Growth of GeSn up to 12% Sn is performed for which preliminary characterization results are given.