利用X射线倒易空间分析精确定位纤锌矿ScxAl1-xN/GaN异质结构的晶格匹配条件
Pinpointing Lattice-Matched Conditions for Wurtzite ScxAl1-xN/GaN Heterostructures with X-Ray Reciprocal Space Analysis
AI总结：
本研究利用X射线倒易空间映射，通过等离子体辅助分子束外延生长不同组分的ScxAl1-xN薄膜，精确定位了其在GaN衬底上的晶格匹配条件（x=0.14），并实现了文献报道中最低的X射线衍射摇摆曲线半高宽。
摘要：
通过全面的X射线倒易空间映射，我们确定了在(0001) GaN上生长的纤锌矿ScxAl1-xN层的精确晶格匹配组分为x = 0.14+/-0.01。采用等离子体辅助分子束外延技术，在c面GaN模板上以微小的组分增量生长了厚度为100 nm的ScxAl1-xN薄膜（x = 0.09 - 0.19）。假设在GaN上共格应变的ScAlN薄膜的c晶格参数随Sc含量线性增加，通过拟合(0002) X射线峰位估算了合金组分，其中Sc含量由卢瑟福背散射光谱法独立测定。由(10-15)衍射的高分辨率X射线衍射测量获得的倒易空间图显示，x = 0.14+/-0.01的ScxAl1-xN薄膜与GaN衬底共格应变，而其他组分则显示出弛豫的证据。对于厚度为300 nm的Sc0.14Al0.86N层，进一步证实了其与GaN的面内晶格匹配。该Sc0.14Al0.86N薄膜(0002)衍射的摇摆曲线半高宽为X弧秒，对应文献中报道的纤锌矿ScAlN薄膜的最低值。
英文摘要：
Using comprehensive x-ray reciprocal space mapping, we establish the precise lattice-matching composition for wurtzite $Sc_xAl_{1-x}N$ layers on (0001) GaN to be x = 0.14+/-0.01. 100-nm thick $Sc_xAl_{1-x}N$ films (x = 0.09 - 0.19) were grown in small composition increments on c-plane GaN templates by plasma-assisted molecular beam epitaxy. The alloy composition was estimated from the fit of the (0002) x-ray peak positions assuming the c-lattice parameter of ScAlN films coherently-strained on GaN increases linearly with Sc-content determined independently by Rutherford Backscattering Spectrometry. Reciprocal space maps obtained from high-resolution x-ray diffraction measurements of the (10-15) reflection reveal that $Sc_xAl_{1-x}N$ films with x = 0.14+/-0.01 are coherently strained with the GaN substrate while the other compositions show evidence of relaxation. The in-plane lattice-matching with GaN is further confirmed for a 300-nm thick $Sc_{0.14}Al_{0.86}N$ layer. The full-width-at-half-maximum of the (0002) reflection rocking curve for this $Sc_{0.14}Al_{0.86}N$ film is 106 arcseconds and corresponds to the lowest value reported in the literature for wurtzite ScAlN films.
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