Critical thickness of InAs grown on misoriented GaAs substrates

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Abstract
We grow InAs layers on (001) on-axis and misoriented GaAs substrates by molecular beam epitaxy, respectively. The critical thickness of each InAs layer is investigated with photoluminescence spectroscopy and transmission electron microscopy (TEM). We show that the critical thickness is significantly influenced by the substrate misorientation. The critical thickness of the InAs layer grown on the GaAs substrate misoriented toward the [11̄0] direction becomes thicker [5 monolayers (ML)] than that (3 ML) of the InAs layers grown on the GaAs substrates (001) on-axis or misoriented toward the [110] direction. The plan-view TEM images show that the islands grown coherently do not coalesce even beyond the on-axis critical thickness (3 ML). The strain energy is calculated based on valence-force-field model to investigate the interaction between dislocation and step in case on misoriented substrate. As results, we show that dislocation has the minimum length above which dislocation can stably exist and that the extra strain energy generated at the cross point of dislocation and step plays an important role in dislocation generation.