Fabrication of ordered nanostructures of compound semiconductors

有序排列的纳米结构组装近年来引起了人们的广泛关注。特别是，在基于自组织过程的有序纳米结构的制造方面已经做出了相当大的努力。本研究的目的是利用在InAs/GaAs (111) a界面形成的周期性错配位错阵列来制备有序的GaAs纳米结构。有报道称，InAs在GaAs (111) a上以一层接一层的模式生长，伴随着界面处失配位错网络的形成。由于具有三角对称的位错是等间距的，它们可以作为有序排列的砷化镓纳米结构的模板。二维金属纳米结构阵列的形成已经在几个系统中得到证实。另一方面，对于半导体，虽然一维排列已被报道，但没有在二维中观察到良好的排列。在本研究中，采用液滴外延生长技术制备了砷化镓纳米岛。在该方法中，在没有As通量的情况下提供Ga分子束，导致在衬底上形成液滴状的Ga团簇。随后，提供As助熔剂，使液滴结晶成砷化镓纳米晶体。我们发现Ga纳米岛在埋藏位错之间的压缩应变区更容易形成。在GaAs纳米岛上添加As4助熔剂制备的GaAs纳米岛也显示出高度的有序性，而同时沉积Ga和As导致GaAs纳米岛的随机成核。因此，该方法使我们能够实现有序的二维排列的砷化镓纳米结构，这是通过同时沉积Ga和As的生长无法实现的。目前的结果将为制造密度可控的有序纳米岛阵列开辟道路

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