Surprising concentrations of hydrogen and deuterium, as high as 5×1020cm−3, were incorporated into nitrogen‐doped ZnSe grown on GaAs by molecular beam epitaxy. Infrared absorption bands due to local vibration modes were observed at 3193 and 783 cm−1for ZnSe:N,H samples, and at 2368 cm−1for ZnSe:N,D samples using Fourier transform infrared spectroscopy. The isotopic shift in the absorption band agrees with predictions of a simple harmonic oscillator approximation for N–H bonding. The variation of the absorption band associated with substitutional nitrogen with nitrogen concentration indicates that not all nitrogen is substitutional, and also exhibited significant changes related to hydrogen incorporation. ©1996 American Institute of Physics.