Amorphous hydrogenated silicon nitride films (a-Si1-xNx:H) can have varied applications in optoelectronics when produced as alloys with a wide range mobility gap. Employing ArF LCVD and using SiH4/NH3 or Si2H6/NH3 as the precursor gases, we have tailored the bandgap (E-g) of this material from 1.6 to 4.9 eV. It was found that Si2H6/NH3 mixture produced highly silicon-rich alloys with compositions below the percolation threshold (x similar to 0.52) of Si-Si bonds and E-g between 1.6 and 2.9 eV, while SiH4/NH3, produced nitrogen-rich alloys (x similar to 0.59) with E-g upto 4.9 eV. This alloy can thus serve as dielectric and passivating films and also as a wide bandgap semiconductor. Correlations of the gap variation with film structure and composition are discussed.