Comparative studies of band structures for biaxial (100)-, (110)-, and (111)strained GeSn: A first-principles calculation with GGA plus U approach
Comparative studies of band structures for biaxial (100)-, (110)-, and (111)strained GeSn: A first-principles calculation with GGA plus U approach
复制标题
双轴 (100)、(110) 和 (111) 应变 GeSn 能带结构的比较研究：使用 GGA 加 U 方法的第一性原理计算
DOI：
10.1063/1.4933394
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发表时间：
2015-10-28
影响因子：
3.2
通讯作者：
Liu, Zhi
中科院分区：
文献类型：
--
作者：
Huang, Wenqi;Cheng, Buwen;Liu, Zhi
在先前的研究中进行的实验和计算表明，压缩应变将增加（100）-应变GeSn的需要Sn实现直接带隙时，它是赝晶生长在Ge缓冲。为了消除这种负面影响，我们系统地研究了双轴（100）-，（110）-和（111）-应变GeSn的能带结构，使用第一性原理计算结合超晶胞模型和GGA垂直杆U方法。该方法已被证明是有效和准确的计算GeSn的性质。计算得到的Ge和Sn的晶格常数和弹性常数与实验结果符合较好。将非应变GeSn的带隙从间接改变为直接所需的Sn浓度的交叉值被发现为8.5%，这与最近的实验结果9%非常接近。对应变GeSn带隙的计算表明，在（100）和（110）应变GeSn中，γ谷的移动速率大于L谷和X谷的移动速率。而在（111）应变GeSn中，L谷的移动速率大于γ谷和X谷。拉伸应变对（100）-和（110）-应变GeSn的转变具有积极影响，将带隙从间接改变为直接，而压缩应变对（111）-应变GeSn具有积极影响。（111）取向的使用可以减少GeSn对Sn的需要，并且大大增加L谷和伽马谷之间的能量差。因此，对于在Ge缓冲层上生长的应变GeSn，（111）取向是利用压缩应变的良好选择。(C)2015 AIP Publishing LLC.
Experiments and calculations performed in previous studies indicate that compressive strain will increase (100)-strained GeSn's need for Sn to realize a direct bandgap when it is pseudomorphically grown on Ge buffers. To eliminate this negative effect, we systematically investigate the band structures of biaxial (100)-, (110)-, and (111)-strained GeSn using a first-principle calculation combined with supercell models and the GGA vertical bar U approach. This method has proven to be efficient and accurate for calculating the properties of GeSn. The calculated lattice constants and elastic constants of Ge and Sn are in good agreement with the experimental results. The crossover value of Sn concentration which is required to change the bandgap of unstrained GeSn from indirect to direct is found to be 8.5%, which is very close to the recent experimental result of 9%. The calculated bandgaps of strained GeSn show that the moving rate of the Gamma valley is higher than those of the L and X valleys in (100)-and (110)-strained GeSn. However, the moving rate of the L valley is higher than those of Gamma and X valleys in (111)-strained GeSn. Tensile strain has a positive effect on the transition of (100)-and (110)-strained GeSn, changing the bandgap from indirect to direct, whereas compressive strain has a positive effect for (111)-strained GeSn. The use of the (111) orientation can reduce GeSn's need for Sn and greatly increase the energy difference between the L valley and Gamma valley. Thus, for strained GeSn grown on Ge buffers, the (111) orientation is a good choice to take advantage of compressive strain. (C) 2015 AIP Publishing LLC.