A study has been made to determine the nature of the acceptor center in laboratory-grown semiconducting diamonds. Analyses for nitrogen, aluminum, boron, and uncompensated-acceptor content of aluminum and boron-doped crystals have shown that (i) the aluminum content of inclusion-free crystals is very low, (ii) there is not enough aluminum to account for the acceptor content, (iii) the nitrogen content is very low and only a small degree of compensation by deep-lying nitrogen donors could exist for many semiconducting diamonds, and (iv) there is a good correlation between boron content and acceptor content. These results indicate that boron is the dominant acceptor in laboratory-grown semiconducting diamond, and not aluminum as has been assumed previously by a number of authors. These results, when combined with other data on resistivity and activation energy for conduction, indicate that the dominant semiconducting properties of both natural and laboratory-grown diamond are due to one acceptor, boron, at different concentrations. Previous papers on laboratory-grown semiconducting diamonds which based arguments on the large aluminum content and the assumed high nitrogen content are critically reexamined.

• Received 6 November 1972

DOI:https://doi.org/10.1103/PhysRevB.7.4560