Cathodoluminescence of phosphorus doped (111) homoepitaxial diamond thin films

A homoepitaxial diamond film with a thickness of approximately 1 μm was grown on the (111) surface of a type Ib diamond substrate with dopant concentration (PH₃/CH₄) of 500 ppm. Bound exciton recombination radiation due to the neutral donors has been observed in the peaks at 5.18 and 5.32 eV. The dominant peak at 5.18 eV is associated with one TO phonon. The peak at 5.32 eV is the radiation without phonon emission due to the localization of donors. This appearance of non-phonon emission is one of the important evidences to prove the two peaks at 5.18 and 5.32 eV to be the recombination radiation of bound exciton due to the donor. The binding energy of the free exciton to the donors, which is deduced from the energy difference between free and bound exciton, is 90 meV.