Spontaneous Nucleation and Growth of GaN Nanowires: The Fundamental Role of Crystal Polarity
Spontaneous Nucleation and Growth of GaN Nanowires: The Fundamental Role of Crystal Polarity
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DOI：
10.1021/nl302664q
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发表时间：
2012-12-01
期刊：
影响因子：
10.8
通讯作者：
Brandt, Oliver
中科院分区：
文献类型：
--
作者：
Fernandez-Garrido, Sergio;Kong, Xiang;Brandt, Oliver
我们通过实验研究了晶体极性是否影响等离子体辅助分子束外延中GaN纳米线的生长，以及它们的形成是否必须由缺陷诱导。为此，我们在6H-SiC（0001）和SiC（000 (1) over bar）衬底上制备了光滑和连贯应变的AlN层，以确保明确的极性和没有结构和形态缺陷。在n极AlN上，形成均匀致密的n极GaN纳米线阵列，证明GaN纳米线在没有缺陷的情况下是自发形成的。在al -极性AlN上，我们没有观察到ga -极性GaN NWs的形成。相反，稀疏的n -极性GaN纳米线嵌入在ga -极性GaN层中。这些n极性氮化镓纳米线被证明是偶然的，因为必要的极性反转是由SixN的形成引起的。因此，目前的发现表明，自发形成的氮化镓纳米线是不可逆转的n极性。由于极性对GaN基器件性能的强烈影响，这些结果不仅对理解GaN纳米线的自发形成至关重要，而且具有很高的技术相关性。
We experimentally investigate whether crystal polarity affects the growth of GaN nanowires in plasma-assisted molecular beam epitaxy and whether their formation has to be induced by defects. For this purpose, we prepare smooth and coherently strained AlN layers on 6H-SiC(0001) and SiC(000 (1) over bar) substrates to ensure a well-defined polarity and an absence of structural and morphological defects. On N-polar AlN, a homogeneous and dense N-polar GaN nanowire array forms, evidencing that GaN nanowires form spontaneously in the absence of defects. On Al-polar AlN, we do not observe the formation of Ga-polar GaN NWs. Instead, sparse N-polar GaN nanowires grow embedded in a Ga-polar GaN layer. These N-polar GaN nanowires are shown to be accidental in that the necessary polarity inversion is induced by the formation of SixN. The present findings thus demonstrate that spontaneously formed GaN nanowires are irrevocably N-polar. Due to the strong impact of the polarity on the properties of GaN-based devices, these results are not only essential to understand the spontaneous formation of GaN nanowires but also of high technological relevance.