Compositional inhomogeneity and strain relaxation in InGaAs SQWs MOVPE-grown on tilted GaAs substrates

The use of tilted substrates produces both strong compositional and thickness inhomogeneities (macrosteps) and an increase of the misfit dislocation density by homogeneous nucleation in MOVPE InGaAs SQWs with respect to the case of exactly oriented substrates. A further increase of the overall dislocation density, including threading dislocations and dislocations inside the layer, is due not only to the increased number of interactions between misfit dislocations but also to the presence of the macrosteps that very likely supply sites for heterogeneous nucleation of misfit dislocations and favour nucleation of dislocations inside the layers. The macrosteps associated with the substrate misorientation also affect the optical properties.