Room-temperature photoluminescence from the GaInNAs/GaAs multiple quantum wells (MQWs), grown on GaAs substrates by Metalorganic Chemical Vapor Deposition (MOCVD), was investigated as a function of the nitrogen composition. An anomalous wavelength shift in the temperature range < 150 K for samples with nitrogen mole fraction > 0.4%, indicates a strong exciton localization effect in the GaInNAs/GaAs MQWs. These localization states arise from nitrogen alloy fluctuation. The thermal activation energy of the MQWs strongly depends on the N composition, in agreement with a large bandgap bowing introduced by N incorporation. Our results indicate that with a N mole fraction of 0.7% in the GaInNAs/GaAs QW, an activation energy of 90 meV is achieved which can improve the thermal characteristics of the device. (C) 2002 Elsevier Science B.V. All rights reserved.