Electroluminescence of silicon pn diode produced by boron implantation

Large improvement of the electroluminescence efficiency was observed from silicon pn diodes prepared by boron implantation. The temperature dependence of the EL and PL of the pn diode shows a different behavior compared to the PL from bulk silicon substrates. Two asymmetric EL bands from trap bands below the free exciton emission band are observed at around 1.065 and 0.92-0.96 eV at low temperature in the silicon pn diode. The intensity of the two bands increases strongly with increasing boron concentration. A blue shift of the two bands with increasing the injection current was observed which is similar to EL in deta-doped semiconductors. The temperature dependence of the EL intensity from the different bands shows that the thermal emission of carriers from these traps is responsible for a strong increase of the band edge radiative emission of silicon. These results are consistent with a rate equation model based on the emission, trapping and recombination processes for a system containing free excitons and bound excitons. Our results give an alternative explanation to the strong increase of the EL efficiency in boron implanted silicon pn diodes [1].
[1] W.L. Ng et al., Nature 410, 192 (2001).