Y3(Al,Ga)5O12:Tb thin films were grown in an O2 working atmosphere on Si (1 0 0) substrates using the pulsed laser deposition (PLD) technique. Micrometer and sub-micrometer sized particulates were present on the surface and inside the Y3(Al,Ga)5O12:Tb thin films. Secondary electron micrographs showed that particulates were present on the surface and X-ray spectrometry mapping showed that the particulates consist of different concentrations of Y, Tb, Ga and Al. Time of flight secondary ion mass spectroscopy results revealed that the as-deposited film was filled with agglomerated particles of Ga and Al of different sizes. The agglomerated Ga particles seemed to be evenly distributed after annealing at 800 °C and the film surface and interface were enriched with Ga after annealing. Atomic force microscopy confirmed the distribution of the agglomerated Ga particles. The region with the evenly distributed Ga showed a surface with a smooth morphology. Shifts in the peak position to lower diffraction angles were observed in the XRD patterns of the annealed film compared to the pattern of the Y3(Al,Ga)5O12:Tb powder. The optical measurements of the Ga enriched film indicated that a new excitation band different from the original Y3(Al,Ga)5O12:Tb powder was obtained.