Fabrication of ordered nanostructures of compound semiconductors

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Assembly of nanostructures with ordered arrangement has attracted substantial recent attention. In particular, considerable efforts have been made for the fabrication of ordered nanostructures based on the self-organized processes. The purpose of this research is to fabricate ordered nanostructures of GaAs using a periodic misfit dislocation array formed at the interface of InAs/GaAs (111)A. It has been reported that InAs grows in a layer-by-layer mode on GaAs (111) A, being accompanied by the formation of the network of misfit dislocations at the interface. Since the dislocations with trigonal symmetry are equally spaced, they can serve as templates for an ordered arrangement of GaAs nanostructures.The formation of two-dimensional nanostructure arrays of metals has been demonstrated in several systems. On the other hand, for semiconductors, although one-dimensional alignment has been reported, no well-ordered arrangement in two dimensions has been observed. In the present study, GaAs nanoislands are fabricated using the growth technique so called droplet epitaxy. In this method, Ga molecular beam is supplied initially without As flux, leading to the formation of droplet-like Ga clusters on the substrate. Subsequently, an As flux is supplied which results in the crystallization of the droplet into GaAs nanocrystal.We found that Ga nanoislands are preferably formed at compressively : strained regions between buried dislocations. GaAs nanoislands fabricated by supplying As4 flux to the Ga islands also show a high degree of ordering, while simultaneous deposition of Ga and As results in random nucleation of GaAs nanoislands. Thus the method allows us to achieve an ordered two-dimensional arrangement of GaAs nanostructures, which could not be realized by the growth from simultaneous deposition of Ga and As. The present results will open the way to fabricate an ordered array of nanoislands with controlled densities