Lattice curvature generation in graded InxGa1-xASGaAs buffer layers

Position dependent lattice tilts in InGaASGaAs(001) compositionally graded buffer layers are investigated. The lateral dependence of the tilt defines a concave buffer layer curvature of up to 3 deg cm-1. The buffer layer curvature is associated with a distribution of the misfit dislocation Burgers vectors that varies nearly linearly across the sample. The origin of this peculiar distribution is discussed and is explained in terms of a Burgers-vector selection rule, which governs the cross slip of gliding threading dislocations and that has been experimentally observed by Capano in Phys. Rev. B 45, 11 768 (1992). A quantitative model of lattice curvature formation is presented that satisfactorily accounts for the main features of the observed buffer layer curvature