Efficient silicon based light emitters

Recently remarkable progress has occurred in the variety and efficiency of silicon based light emitters, based on Si pn junctions, Si MOS structures doped with rare earth elements, or containing Si nanoclusters. I will present our work in some of these areas.

We have fabricated Si light emitting diodes (LED) by high-dose boron implantation into n-type Si. The free-exciton electroluminescence (EL) increases with temperature, reaching wall-plug efficiencies of more than 0.1% at room temperature. A model which is based on excitons localized near nanoscale boron doping spikes can explain the EL dependence on current and temperature. We have integrated such structures into a microcavity with a buried metallic CoSi2 bottom mirror and a Si/SiO2 Bragg mirror on top. This resonant-cavity LED exhibits significant spectral narrowing, consistent with the quality of the cavity.

We also have fabricated light emitting Si MOS structures which were implanted with various rare-earth elements, from the well known Er3+ emitting at the telecom wavelength of 1.54 microns, to Gd3+, which emits in the deep UV at 316 nm. This is, to our knowledge, the first Si based UV light emitter, with many potential applications in areas such as bio-sensing.