We report on the investigation of the effects of rapid thermal annealing (RTA) on the optical and structural properties of InxGa1-xP1-yNy alloys (x = 0.176 and 0 <= y <= 0.087) on GaP grown by metalorganic vapor phase epitaxy (MOVPE). Photoluminescence (PL) and PL excitation (PLE) spectroscopies were carried out to measure the energy positions of the near band edge excitonic emission. The high-resolution X-ray diffraction (HRXRD) measurements were carried out to examine the changes in the N concentration after RTA at 750 degrees C for 30 s. For y < 0.074, the RTA treatment induces a large blue-shift of the PL peak energy and the absorption edge of PLE, which indicates some structural modification of these alloy films. On the other hand, for y >= 0.074, both the PL and PLE spectral features remain qualitatively identical after RTA, suggesting the unchanged recombination mechanism. Furthermore, HRXRD results confirmed that the InxGa1-xP1-yNy closely lattice-matched films are thermally more stable against the N out diffusion. (c) 2006 Elsevier B.V. All rights reserved.