Ge-Ga-S glasses, contrary to other well-known chalcogenide glasses, show high rare-earth solubility. Raman spectra of GeS2-Ga2S3 glasses showed that two peaks at 260 cm-1 and 385 cm-1 increased in intensity with the addition of Ga2S3. These peaks are associated with the vibration of Ge-Ge bonds and edge-shared [GsS4] tetrahedra, respectively. In GeS2-Ga2S3-La2S3 glasses, the peak at 260 cm-1 decreased in intensity with addition of La2S3 and the one at 375 cm-1 due to the vibration of tetrahedra with non-bridging sulfurs increased. It indicated that La, or rare-earths in general, can easily be dissolved into the glass network as charge compensators for non-bridging sulfurs which were formed through the dissociation of Ge-Ge bonds and edge-shared [GaS4] tetrahedra. Since no such structural modification is expected in glasses as Ga-As-S, these peculiar transitions on the connection scheme in Ga-containing chalcogenide glasses seem to be playing the most important role on the enhanced rare-earth solubility.