We have found that antimony (Sb) plays an important role for the improvement of optical properties of the GaInNAs/GaAs quantum well in the 1.3 mum region grown by metalorganic vapor-phase epitaxy. Non-annealed samples grown with pre-flow of trimethylantimony (TMSb) showed good optical properties equivalent to that of annealed samples grown without TMSb. These samples showed higher tolerance to thermal annealing and maintained good photoluminescence (PL) intensity up to 720degreesC. The atomic force microscope image showed the improvement of surface smoothness. These results suggest supplying TMSb only before the growth of the quantum well is effective for the improvement of interface between GaInNAs and GaAs. (C) 2004 Published by Elsevier B.V.