X-ray diffraction topographs made with synchrotron radiation of an epitaxial InAs structure show images of dislocations and stacking faults. Three types of dislocations are identified and their Burgers vectors are determined from a number of topographs having different diffraction vectors and recorded on the same film at a time. Straight dislocations are found to be edge dislocations and their Burgers vector is (110). Also mixed dislocations are found. The overall dislocation density is about 2000 cm(-2). Large stacking faults are limited by long straight dislocations, the Burgers vector of which is (110). Only a few threading dislocations are observed in the epitaxial layer grown by vapourphase epitaxy. Their density is about 500 cm(-2). Small circular dots found are interpreted as indium-rich inclusions. (c) 2005 Elsevier B.V. All rights reserved.