Electroluminescence of self-assembled Ge hut clusters

We have fabricated Si-based light-emitting diodes operating in the near infrared. The active layers of the devices consist of either one or ten layers of Ge/Si self-assembled hut clusters grown by molecular-beam epitaxy. Luminescence is observed in the spectral range between 1.4 and 1.5 μm. For the ten layer stack of Ge islands, electroluminescence is observed up to room temperature. A direct comparison with a pure Si reference p-i-n diode allows us to attribute the luminescence to radiative recombinations between holes localized in the Ge islands and electrons localized in the strained Si above and below the islands.