Electrically tunable Si-based three-color light-emitting diode

We demonstrate a three-color tunable light-emitting diode in the near-infrared region based on a pseudomorphic Si1−xGex/Si triple quantum well. The emission color is tuned by controlling real space transfer of electrons under longitudinal electric fields. Emission occurs each time electrons preferentially populate one of the quantum wells harboring the quantum-confined holes. A key advance compared with our earlier two-color devices is the selective activation of the center quantum well through dynamically programmed electron trapping, which allows full three-color operation within a single chip. The device further exhibits ambipolar behavior, combining forward-biased injection and impact ionization-assisted emission under reverse bias.