Influence of compositional macrosteps on the reduction of the critical thickness by generation of <010> misfit dislocations in InGaAs/GaAs quantum wells

A reduction of the critical thickness has been seen to occur in InGaAs single quantum wells grown by MOVPE on tilted GaAs substrates by the generation of Ž010 aligned misfit dislocations. The latter ones have been generated by glide of half loops on {110} planes instead of the usual {111} slip planes. The single quantum wells also contain compositional macrosteps which produce periodic thickness oscillations giving rise to a ripple morphology of the layer surface. Since the glide of half loops in the secondary {110} slip planes can occur only under conditions of high strain, it is hypothesized that their propagation, hence the formation of Ž010 misfit dislocations, takes place at the observed compositional macrosteps where enhanced concentration of strain is likely to occur.