On the Origin of Strain Relaxation in MOVPE InGaAs/GaAs SQWs by <010> Aligned Misfit Dislocations

<010> aligned misfit dislocations are found to start strain relaxation at a reduced critical thickness in (100) InGaAs SQWs grown on misoriented GaAs substrates. The InGaAs layers also contain In content inhomogeneities (compositional macrosteps) that give rise to thickness fluctuations. Since the formation of the <010> misfit dislocations requires high strain, as it needs glide of half loops on the {110} planes, it is argued that it is due to the observed compositional macrosteps as they can be sites of enhanced strain concentration.