The GaAsN films have been grown on GaAs(100), (111)A, (111)B and (011) substrates at 550 degrees C by metalorganic vapor-phase epitaxy (MOVPE) to investigate the substrate orientation dependence of the N content. The N content of the GaAsN films estimated from X-ray diffraction (XRD), photoluminescence (PL) and secondary ion mass spectrometry (SIMS) was fairly consistent. At the As/III ratio of 20, the N content is in the order (111)A > (100) > (011)similar to(111)B similar to 0, which is the same order as that expected from the strain energy arising from the N incorporation. When the tertiarybutylarsine's (TBA's) flow rate is decreased down to the As/III ratio of 5 while the trimethylgallium (TMGa) and 1,1-dimethylhydrazine (DMHy) flow rates are constant, the N content for (111)B and (011), as well as (100) is increased whereas that for (111)A is almost unchanged, resulting in the order (100) > (111)A > (111)B > (011). These results may be attributed to the balance between the strain energy and the N desorption efficiency, which will be changed with the coverage of As on the surface. (c) 2006 Elsevier B.V. All rights reserved.