Near-Band-Edge Luminescence Studies of Diamond Doped during CVD Growth or by Ion Implantation

Abstract

Near-band-edge cathodoluminescence of doped diamonds was studied at low temperatures. The doped diamonds were prepared either during the CVD growth of the diamond films by adding boron, phosphorus, or lithium sources to the reaction gases, or alternatively by ion implantation of boron, phosphorus, sodium, or arsenic. Observation of the boron bound exciton after boron implantation and annealing above 1200 °C is taken as evidence that this acceptor species was successfully incorporated on substitutional lattice sites. Similarly, doping by phosphorus either during growth or by ion implantation and subsequent annealing leads to the emission of a bound exciton transition at 5.175 eV. Assuming Haynes' rule to be valid we estimate a donor ionization energy of nearly 640 meV for the phosphorus-related impurity. Discrete donor–acceptor pair transitions are observed in the near-band-edge region in diamonds which contain both phosphorus and boron in low concentrations. The analysis of the spectra yields 630 meV activation energy of the phosphorus-related donor consistent with the estimate from the bound exciton spectra.