Electronic properties of the (100) (Si)/(Ge) strained-layer superlattices.
Electronic properties of the (100) (Si)/(Ge) strained-layer superlattices.
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(100) (Si)/(Ge) 应变层超晶格的电子特性。
DOI：
10.1103/physrevb.38.13237
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
C. G. V. D. Walle
中科院分区：
文献类型：
--
作者：
S. Satpathy;Richard M. Martin;C. G. V. D. Walle
通过局域密度赝势计算，我们研究了（Si）n/（Ge）m（n，m = 3-7）应变层超晶格的电子结构，并显示了应变和层厚如何相互作用决定电子态的性质.用群论方法讨论了电子态的对称性，并分析了偶极允许光跃迁的选择规则。对于已报道实验的（Si）_4/（s-Ge）_4（其中s表示应变）超晶格，我们发现在0.76eV处观察到的最低能量跃迁不是直接跃迁。从对称性考虑，在1.1eV处的最低直接跃迁在光学上是不允许的，最低允许的直接跃迁发生在1.2eV处。超晶格层中的应变被证明对差距区域中的电子态的性质具有重要的影响。我们表明，薄的超晶格生长在Ge或Si-Ge合金衬底是有前途的候选人的直接带隙材料。
By performing local-density pseudopotential calculations, we examine the electronic structure of the (Si) n/(Ge) m (n, m∼ 3–7) strained-layer superlattices and show how strain and the layer thicknesses interplay in determining the nature of the electron states. A group-theoretical discussion of the symmetry properties of the electron states as well as an analysis of the selection rules for dipole-allowed optical transitions are given. For the (Si) 4/(s-Ge) 4 (where s denotes strained) superlattice on which experiments have been reported, we find that the lowest-energy transition observed at 0.76 eV is not a direct transition. The lowest direct transition at∼ 1.1 eV is not optically allowed from symmetry considerations, with the lowest allowed direct transition occurring at∼ 1.2 eV. Strain in the superlattice layers is shown to have an important effect on the nature of electron states in the gap region. We show that thin superlattices grown on Ge or Si-Ge alloy substrates are promising candidates for direct band-gap materials.