Optical evidence for 630-meV phosphorus donor in synthetic diamond

Abstract

Diamond samples doped with phosphorus either during high-pressure/high-temperature synthesis or during chemical vapor deposition growth are studied by cathodoluminescence at low temperatures. Some of the specimens unintentionally contain boron acceptors in low concentrations as demonstrated by the observation of boron-bound exciton emission at 5.215 eV. Other samples show a lower energy-bound exciton line at 5.175 eV relating in intensity to the phosphorus concentration and indicative of a phosphorus impurity or a phosphorus complex. Four samples phosphorus doped by different techniques reveal almost identical discrete donor-acceptor pair-line spectra between 5.2 and 4.7 eV. The appearance of these spectra gives firm evidence for a phosphorus-related donor. Analysis of the spectra assuming boron as the acceptor involved yields an ionization energy of $(630\ifmmode\pm\else\textpm\fi{}50)$ meV for the phosphorus donor.