Green and near-infrared luminescence due to the biexcitons in unperturbed silicon

We have used an ultrasensitive imaging photomultiplier tube to study the green luminescence (caused by the complete no-phonon annihilation of a biexciton to yield one photon) occurring at approximately twice the Si band-gap energy. The binding energy of the biexciton relative to the lowest energy-free exciton edge was found to be 1.36±{} 0.26 meV, in good agreement with an earlier measurement based on the near-infrared biexciton spectrum. Recent attempts to call those earlier results into question are shown to be unfounded.