Excited neutral nitrogen species emitted from a rf plasma source were characterized by the laser-induced fluorescence (LIF) spectroscopy, while nitrogen ions were detected by the ion counting method. The LIF intensity for nitrogen molecules increases monotonously up to the rf power of 100 W and saturates over 100 W. On the contrary, ion count of nitrogen ions shows a gradual increase up to 100 W, then rapidly increases above 100 W. The correlation between the number of excited nitrogen species and the net acceptor concentration(NA−ND)of nitrogen doped ZnSe epitaxial layers for various rf powers has been studied. We confirm that the excited neutral nitrogen molecules are effective for acceptor doping, while nitrogen ions enhance carrier compensation presumably due to degradation of crystal quality. We show that the activation ratio{(NA−ND)/[N]}ofp-ZnSe:N is greatly improved by removing ions from the nitrogen plasma. ©1997 American Institute of Physics.