The InAsN epilayers have been successfully grown on GaAs (0 0 1) substrates with a similar to 0.8-mum-thick InAs buffer layer by radio-frequency plasma-source molecular beam epitaxy. A series of samples obtained at different growth temperatures have been analyzed by high-resolution X-ray diffraction and atomic force microscopy to characterize the structural properties. The strain and the nitrogen concentration of the InAsN epilayers grown on InAs (0 0 1) substrates have also been evaluated for application to those on the InAs buffer layer on the GaAs substrates. The maximum nitrogen concentration of the epilayers grown on the GaAs substrate was estimated to be 1.62% when the growth temperature was 420degreesC. (C) 2002 Elsevier Science B.V. All rights reserved.