Strain-Induced Band Gap Engineering in Selectively Grown GaN-(Al,Ga)N Core-Shell Nanowire Heterostructures
Strain-Induced Band Gap Engineering in Selectively Grown GaN-(Al,Ga)N Core-Shell Nanowire Heterostructures
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DOI：
10.1021/acs.nanolett.6b03354
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发表时间：
2016-11-01
期刊：
影响因子：
10.8
通讯作者：
Stutzmann, Martin
中科院分区：
文献类型：
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作者：
Hetzl, Martin;Kraut, Max;Stutzmann, Martin
我们展示了直接在Si（111）上选择性区域生长GaN-（Al，Ga）N核壳纳米线异质结构。光致发光光谱上生长的纳米线揭示了一个强大的蓝移的GaN带隙从3.40至3.64 eV在室温下。拉曼测量将这种位移与GaN芯内的压缩应变相关联。在纳米尺度上，阴极发光光谱和扫描透射电子显微镜证明了均匀的应变相关发光沿着的纳米线轴和壳内没有显着的波动，分别。实验结果与数值模拟的比较表明，所有研究的结构都没有明显的缺陷相关应变弛豫，壳厚度为50 nm时最大压缩应变为-3.4%。通过选择性区域生长精确控制纳米线尺寸，即芯直径、壳厚度和纳米线周期，允许对同一样品上的各个纳米线内的所得应变进行特定操纵。这又使得能够在一步生长过程中以240 meV的能量范围对GaN带隙进行空间分辨调整。
We demonstrate the selective area growth of GaN-(Al,Ga)N core shell nanowire heterostructures directly on Si(111). Photoluminescence spectroscopy on as-grown nanowires reveals a strong blueshift of the GaN band gap from 3.40 to 3.64 eV at room temperature. Raman measurements relate this shift to compressive strain within the GaN core. On the nanoscale, cathodoluminescence spectroscopy and scanning transmission electron microscopy prove the homogeneity of strain-related luminescence along the nanowire axis and the absence of significant fluctuations within the shell, respectively. A comparison of the experimental findings with numerical simulations indicates the absence of a significant defect-related strain relaxation for all investigated structures, with a maximum compressive strain of -3.4% for a shell thickness of 50 nm. The accurate control of the nanowire dimensions, namely, core diameter, shell thickness, and nanowire period, via selective area growth allows a specific manipulation of the resulting strain within individual nanowires on the same sample. This, in turn, enables a spatially resolved adjustment of the GaN band gap with an energy range of 240 meV in a one-step growth process.