We produce amorphous terbium doped wide bandgap semiconductor thin films of the pseudobinary compound (SiC)1-x(AlN)x by rf triple magnetron sputtering. Cathodoluminescence measurements performed at samples having different compositions x show pronounced intra 4f shell transition peaks of the trivalent terbium. Thermal activation of the terbium emission by isochronal annealing of the films leads to a strong increase in emission intensity. © (2010) Trans Tech Publications.