Modulation of the electronic transitions of silicon light-emitting diodes produced by boron implantation

Two asymmetric electroluminescence bands with tunable maxima at around 1.044-1.065 and 0.90-1.00 eV are observed at low temperature in silicon pn diodes prepared by boron ion implantation and subsequent high temperature annealing. The intensity of the two bands increases strongly with increasing the boron concentration above the solubility. A large blue shift of the two bands with increasing the injection carrier concentration was attributed to the three-dimensional confinement of holes in p-type doped spikes localized on a nanometer scale. They are produced by the boron clustering at the end of range defects close to the pn junction. The two bands with a smaller binding energy is attributed to the spatially indirect recombination of the excitons confined around the strain-free p-type doped spike. The band with a higher binding energy is associated with highly strained p-type doped spikes around dislocations. A significant enhancement of the room temperature electroluminescence efficiency of the silicon diode is observed which is attributed to the spatial modulation of the band structure around these p-type doped spikes.