The structural investigations of thick unclopecl GaInNAs/GaAs heterostructures grown by atmospheric pressure vapor phase epitaxy (AP-MOVPE) have been performed by transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The cross-sectional view TEM images revealed plainly heterogeneous layer structure, consisting of a few sublayers with different indium and nitrogen contents. On the other hand, planar-view TEM images revealed 2D network of misfit dislocations oriented in two orthogonal < 010 > crystallographic directions at the (001) sublayer interface. Moreover, the XRD measurements provide information about gradient profiles of indium and nitrogen contents, as well as distinct anisotropy of strain relaxation in GaInNAs epitaxial layer, evoked by the asymmetry in formation of interfacial misfit dislocation. The obtained results were exploited to calculate the band structure diagram of the investigated GaInNAs/GaAs heterostructure and mean values of the lattice parameters of the distorted epitaxial layer unit cell, respectively. (C) 2015 Elsevier B.V. All rights reserved.