The potential of GaAs-based dilute nitride alloys, such as GaNAs and GaInNAs, for use in long-wavelength telecommunication applications has led to intensive research into their growth and physical properties. In order to produce high quality GaNAs-based devices it is essential that the material and growth source is fully characterised. In this paper, we present a study of MBE grown dilute GaNxAs1-x(x approximate to 0.01) structures grown using two different nitrogen RF-plasma sources. The samples have been characterised using low energy secondary ion mass spectrometry (SIMS), whilst the attributes of the RF-plasma sources have also been fully assessed with this analytical technique. The study shows that low energy SIMS is essential in order to fully characterise the structure and purity of the GaNAs superlattices grown and can also assist in qualification of the RF-plasma source used for growth. (c) 2006 Elsevier B.V. All rights reserved.