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 technology(1). Although several approaches are being explored(1-6), all presently suffer from low emission efficiencies, with values in the 0.01-0.1% range regarded as high(2). 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 ago(7,8). 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.