Efficient silicon light-emitting diodes

Considerable effort is being expended on the development of efficient silicon light-emitting devices compatible with silicon-based integrated circuit technology1. Although several approaches are being explored1,2,3,4,5,6, all presently suffer from low emission efficiencies, with values in the 0.01–0.1% range regarded as high2. Here we report a large increase in silicon light-emitting diode power conversion efficiency to values above 1% near room temperature—close to the values of representative direct bandgap emitters of a little more than a decade ago7,8. Our devices are based on normally weak one- and two-phonon assisted sub-bandgap light-emission processes. Their design takes advantage of the reciprocity between light absorption and emission by maximizing absorption at relevant sub-bandgap wavelengths while reducing the scope for parasitic non-radiative recombination within the diode. Each feature individually is shown to improve the emission efficiency by a factor of ten, which accounts for the improvement by a factor of one hundred on the efficiency of baseline devices.