Gallium indium sulfide thin films with different compositions were deposited on soda-lime glass substrates at 350 and 450 °C by modulated flux deposition. Pure indium sulfide layers consisted of (1 0 3)-oriented beta-In2S3 and reached the widest bandgap, with Eg ~ 2.6 eV. The films became amorphous when a minimum amount of gallium was incorporated. At atomic ratios Ga/In~1, beta-In2S3 and beta-GaS weak diffraction lines were observed; an increase in the supply of sulfur led to thicker, more sulfur-rich and nearly amorphous layers. A further addition of gallium induced the disappearance of beta-In2S3, while beta-GaS remained at the highest preparation temperature. In general, the preparation conditions had a small influence on the optical bandgap.