GaNxAs1-x multiple-quantum-well (MQW) samples (x <= 0.025) grown by molecular beam epitaxy have been studied by photolummescence (PL) spectroscopy, high-resolution X-ray diffraction (HR-XRD), secondary-ion mass spectrometry (SIMS) and ultra-high-resolution infrared local-vibrational-mode (IR LVM) spectroscopy in order to determine their compositional and structural properties. Compositional data from PL spectroscopy and HR-XRD, derived using simple models of the superlattice structure, show good agreement. SIMS depth profiles show that the wells are triangular, and are wider and shallower than predicted, with nitrogen present in the barrier layers. A comparison between SIMS and HR-XRD suggests the presence of interstitial nitrogen for samples with the highest nominal concentrations. By contrast, IR LVM measurements demonstrate that substitutional nitrogen incorporates linearly with increasing nitrogen fraction. (c) 2006 Elsevier B.V. All rights reserved.