Efficient silicon light emitting diodes by boron implantation: the mechanism

Experiments and theoretical modeling are presented on the origin of efficient electroluminescence from boron implanted Si-LEDs. At low lattice temperatures two bound exciton traps created by high dose boron implantation were observed in the most efficient LEDs with external power efficiency above 0.12%. The temperature dependence of the correlation between the EL intensity from free and bound excitons is analyzed by a rate equation model. This analysis reveals that the bound excitons have a unique characteristic of a low recombination rate. The enhancement of EL from free electron-hole pairs with increasing temperature is due to the thermal activation of carriers from bound exciton traps.