Anisotropic strain relaxation and surface morphology related to asymmetry in the formation of misfit dislocations in InGaAs/GaAs heterostructures

Partially relaxed InGaAs/GaAs heterostructures with a small lattice mismatch (less than 1%), grown by metalorganic vapour-phase epitaxy have been studied by the transmission electron microscopy, atomic force microscopy as well as X-ray diffractometry. A regular network of 60st.?misfit dislocations formed at the (001) interface in two orthogonal <110>?crystallographic directions has been revealed. A close correspondence between distribution of the interfacial misfit dislocations and undulating surface morphology in the form of a characteristic cross-hatch pattern has been observed. The structural analysis applied for the samples oriented either in [110] or [110] perpendicular directions, using reciprocal lattice mapping, revealed anisotropic strain relaxation, related to the asymmetry in the formation of alfa ?and beta ?misfit dislocations along these both directions, respectively.