Efficient light emitting devices based on nanoscale silicon

Recently some remarkable advances concerning silicon based light emission have been reported. This has triggered the hope that a practical Si based light source may soon become reality. Several approaches are pursued by research groups worldwide: porous Si, Si nanocrystals and Er3+ in SiO2, Er3+ doped Si, Si/Ge quantum cascade structures, and also more “conventional” Si pn diodes. I will give a survey on some of these approaches and then concentrate on Si pn diodes, fabricated by high-dose boron implantation.

In these structures the electroluminescence (EL) increases with temperature, resulting in a wall-plug efficiency of 0.1% at room temperature. Extensive low-temperature EL measurements allow us to put forward a model, which is based on the interplay between free excitons/carriers and excitons localized at nanoscale boron doping spikes, similar to delta-doped layers produced by MBE. Within this model we are able to explain the EL dependence on current and temperature, as well as an electrical bistability occurring at low temperature. Finally, we have fabricated what is, to our knowledge, the first electrically driven resonant-cavity LED based on silicon.