A Fabry-Perot microcavity is used for the enhancement and inhibition of photoluminescence in hydrogenated amorphous silicon nitride. The amplitude of the photoluminescence is enhanced 4 times, while its linewidth is reduced 8 times with respect to the bulk hydrogenated amorphous silicon nitride. The transmittance, reflectance, and absorptance spectra of the microcavity were also measured and calculated. The calculated spectra agree well with the experimental ones.