We report a detailed study of the localized carrier effect and optical characterization of the novel dilute-nitride GaInNP films. These films were grown by metal-organic vapor phase epitaxy on GaAs (100) substrates. These epitaxial layers were then characterized by a high-resolution X-ray rocking curve (XRC) and photoluminescence (PL) spectra. With nitrogen incorporation, the PL peak red shifts, indicating bandgap reduction, and the line width broadening increases due to the increase of non-radiative centers. The S-shape in temperature dependence of the PL spectra shows a considerable number of carriers detrap from localized states to higher bound exciton states as the increasing temperature. The PR spectrum is used to confirm the nitrogen induced localization. Furthermore, this localization phenomenon observed in low-temperature PL no longer exists after RTA process. This result suggests that the crystal quality is improved significantly by thermal treatment. (C) 2004 Elsevier B.V. All rights reserved.