Electroluminescence from bound excitons in silicon

We demonstrate a signature of bound-exciton emission in the electroluminescence spectra of wafer-bonded silicon p–n junction, along with the more common free-exciton emissions. The emission is driven by the electric current through a p–n junction formed by direct bonding of p-type and n-type Si wafers, with a thin oxide layer between them. A significant change was observed in the photoluminescence spectrum of the P-doped (n-type) wafers after the bonding. Three new peaks appear at 1097, 1100, and 1136 nm. Their spectral widths closely correspond to those of impurity-bound excitons.