The temperature dependence of optical properties of Ga0.3In0.7NxAs1-x quantum dots (QDs) grown by gas-source molecular beam epitaxy has been investigated using photoluminescence (PL) spectroscopy in the temperature range from 10 to 300 K. Unlike Ga0.7In0.3NxAs1-x quantum wells, these Ga0.3In0.7NxAs1-x QDs exhibit no S-shaped temperature dependence of the PL peak due to localized states, indicating that emission comes from the ground state, not from defect-related localized states. Thermal quenching of the integrated PL intensity is observed at temperatures over 50 K. The activation energy of Ga0.3In0.7NxAs1-x QDs decreases with an increase in nitrogen composition, contrary to the expectation that it would increase due to lowering of the GaInNAs conduction band. Moreover, the activation energy is much smaller than the difference in energy between the ground state and the wetting-layer state, indicating that the activation energy of Ga0.3In0.7NxAs1-x QDs corresponds to nonradiative recombination processes due to nitrogen incorporation. These defect-related states can be reduced by rapid thermal annealing. (C) 2004 American Vacuum Society.