Efficient Light Emission from Hexagonal SiGe

Silicon and Germanium have an indirect band gap, which limits their use in optoelectronic devices. Here, we show that we can create a direct band gap in Si 1-x Ge x alloys by changing the crystal structure from cubic to hexagonal. DFT calculations predict a strong optical transition for 0.65 1-x Ge x alloys have been fabricated and efficient light emission has been observed.