GeSn heterojunction LEDs on Si substrates

GeSn on Si light-emitting diodes (LEDs) is investigated for different Sn concentrations up to 4.2% and they are compared with an LED made from pure Ge on Si. The LEDs are realized from in-situ doped pin junctions in GeSn on Ge virtual substrates. The device structures are grown with a special ultra-low temperature molecular beam epitaxy process. All LEDs clearly show direct bandgap electroluminescence emission at room temperature. The light intensity of the compressively strained GeSn LEDs increases with higher Sn concentration. The in-plane strain of the LEDs is determined with reciprocal space mapping. The bandgap energies of the emitting GeSn layer are calculated from the emission spectra