COMPOSITIONAL INHOMOGENEITY AND STRAIN RELAXATION IN INGAAS SQWS MOVPE-GROWN ON TILTED GAAS SUBSTRATES

The use of tilled substrates produces both strong compositional and th ickness inhomogeneities (macrosteps) and an increase of the misfit dis location density by homogeneous nucleation in MOVPE InGaAs SQWs with r espect to the case of exactly oriented substrates. A further increase of the overall dislocation density, including threading dislocations a nd dislocations inside the layer, is due not only to the increased num ber of interactions between misfit dislocations but also to the presen ce of the macrosteps that very likely supply sites for heterogeneous n ucleation of misfit dislocations and favour nucleation of dislocations inside the layers. The macrosteps associated with the substrate misor ientation also affect the optical properties. (C) 1997 Elsevier Scienc e S.A.