The effect of strain on GaAs1-xNx grown on GaAs is observed using two-dimensional  high-resolution x-ray diffraction rocking curves. The instance when the epilayer changes from a highly strained to a relaxed state, is captured and a change in peak profile is observed. The increase of growth rate is found to have an effect of maintaining the crystal quality and surface reconstruction. Interstitial N complex lowers the tensile strain due to its compressive nature, thereby increasing the critical thickness at high N%. We demonstrated that GaAs0.952N0.048 can be coherently grown to 100 nm on GaAs, exceeding the critical thickness by 4.7 times after an optimization of III–V–N growth by means of higher rf power compensation under an increased growth rate. © 2003 American Institute of Physics.