STUDIES OF METAMORPHIC III-V HETEROSTRUCTURES BY DIGITAL PROCESSING OF HREM IMAGES

The crystalline structures of metamorphic III-V heterostructures, GaSb /(001)GaAs and GaAs/(001)InP, have been studied by image analyses of h igh resolution electron microscopy (HREM) micrographs. Digital process ing has been performed in order to evaluate the extension of the disto rted zone between the substrate and the fully relaxed epilayer. GaSb g rown by MBE at 470 degrees C on GaAs is known to be perfectly relaxed by a Lomer dislocation network directly created during the island grow th. The transition zone is measured to be few atomic planes thick. For the GaAs, grown on InP by MBE at 450 degrees C, the thickness of the transition zone observed at the interface is IO nm. The misfit disloca tion network involved in the relaxation process appears to be poorly o rganized with mainly partial and 60 degrees dislocations. (C) 1998 Els evier Science S.A.