We have investigated effects of a trimethylantimony (TMSb) flow to the interface between GaAs buffer layer and InGaAsN quantum-well layer on localization of carriers in InGaAsN/GaAs single quantum wells (SQWs) grown by metal organic vapor phase epitaxy from the viewpoint of photoluminescence (PL) properties. We also measured photo reflectance spectroscopy in order to determine the energy of the band-edge transition. The Stokes shift of the PL-peak energy under a weak excitation condition decreases from 20 meV in no TMSb flow to 15 meV in the TMSb flow of 5 x 10(-7) mol/min. The PL-decay time in the low-energy PL tail related to localized states is obviously shortened by the TMSb flow. The decay profiles detected at various energies can be explained by a stretched exponential form peculiar to disordered systems. The overall results of the PL characterization demonstrate that the carrier localization is reduced by the TMSb flow to the interface. (c) 2006 Elsevier B.V. All rights reserved.