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 〈010〉 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 〈010〉 misfit dislocations, takes place at the observed compositional macrosteps where enhanced concentration of strain is likely to occur.