Origin of anomalous temperature dependence and high efficiency of silicon light-emitting diodes

Efficient electroluminescence with power efficiency up to 0.12 % is observed from silicon pn diodes prepared by boron implantation with boron concentrations above the solubility limit at the post-implantation annealing temperature. The electroluminescence spectra exhibit a transition from two bound-exciton bands towards the free electron-hole pair recombination with an anomalous increase in the total intensity with increasing temperature. The implantation dose and temperature dependences of the relative peak intensities provide evidence for the relevance of excitonic traps as a supply for free electron-hole pairs and thus the origin of the enhanced electroluminescence at elevated temperatures.