Near-band-edge luminescence studies of diamond doped during CVD growth or by ion implantation

Near-band-edge cathodoluminescence of doped diamonds was studied at low tem peratures. The doped diamonds were prepared either during the CVD growth of the diamond films by adding boron, phosphorus, or lithium sources to the r eaction gases, or alternatively by ion implantation of boron, phosphorus, s odium, or arsenic. Observation of the boron bound exciton after boron impla ntation and annealing above 1200 degrees C is taken as evidence that this a cceptor species was successfully incorporated on substitutional lattice sit es. Similarly, doping by phosphorus either during growth or by ion implanta tion and subsequent annealing leads to the emission of a bound exciton tran sition at 5.175 eV. Assuming Haynes' rule to be valid we estimate a donor i onization energy of nearly 640 meV for the phosphorus-related impurity. Dis crete donor-acceptor pair transitions are observed in the near-band-edge re gion in diamonds which contain both phosphorus and boron in low concentrati ons. The analysis of the spectra yields 630 meV activation energy of the ph osphorus-related donor consistent with the estimate from the bound exciton spectra.