Bound exciton luminescence related to phosphorus donors in CVD diamond

We have studied by low-temperature cathodoluminescence phosphorus-doped CVD diamond films grown on synthetic high-pressure (1 1 1) diamond substrates. A perfect phosphorus-bound exciton spectrum is observed at very high intensity and exorbitantly narrow line widths down to 2.0 meV showing no-phonon (NP)- and wave vector-conserving TA-, TO-, LO-, and (TO+OΓ)-phonon transitions. All lines are split into up to five components, which are well resolved in the sharp NP-transition. Temperature-controlled measurements demonstrate that the line splittings are in the upper excitonic state. At 5.38 eV, only 26 meV below the excitonic gap, we detect a novel, very shallow line spectrum with spectral features characteristic of an isoelectronically bound exciton. Our data are consistent with the isoelectronic trap being a phosphorus donor–boron acceptor pair on close lattice sites. We discuss this model in the light of previous data from GaP and Si isoelectronic centers. [Copyright &y& Elsevier]