Two‐step excitation of photoluminescence in GaP

Donor‐acceptor pair luminescence and radiation of bound excitons have been excited in GaP using radiation with photon energies lower than the band gap. This anti‐Stokes luminescence is explained by a two‐step excitation process via the deep donor oxygen. Excitation with radiation lower than the band gap results in a very low homogeneous excitation density throughout the bulk of the sample and enables the investigation of the phonon structure of the donor‐acceptor pair bands.