A detailed photoluminescence (PL) study reveals that the low-temperature PL
emission in GaNAs epilayers and GaAs/GaNxAs1-x quantum well structures gro
wn by molecular beam epitaxy is governed by recombination of localized exci
tons. This conclusion is based on the analysis of the PL lineshape, its dep
endence on the excitation power and measurement temperature, as well as PL
transient data. The depth of the localization potential is estimated as abo
ut 60 meV, varying slightly among the different structures.