Based on the results of the temperature-dependentphotoluminescence (PL) measurements, the broad PL emission in thephase-separated GaNP alloys with P compositions of 0.03, 0.07, and 0.15has investigated. The broad PL peaks at 2.18, 2.12 and 1.83 eV areassigned to be an emission from the optical transitions from severaltrap levels, possibly the iso-electronic trap levels related tonitrogen. With the increasing P composition (from 0.03 to 0.15), theseiso-electronic trap levels are shown to become resonant with theconduction band of the alloy and thus optically inactive, leading to theapparent red shift (80–160 meV) of the PL peak energy and the trend ofthe red shift is strengthened. No PL emission peak is observed from theGaN-rich GaNP region, suggesting that the photogenerated carriers in theGaN-rich GaNP region may recombine with each other via non-radiationtransitions.