论文标题
化学计量和应变对GE $ _ {1-x} $ sn $ _ {x} $合金计算的影响
Impact of stoichiometry and strain on Ge$_{1-x}$Sn$_{x}$ alloys from first principles calculations
论文作者
论文摘要
我们使用密度函数理论（DFT）计算出葡萄晶键的电子结构（ge $ _ {1-x} $ sn $ _ {x} $）二进制合金。确定了具有半导体或半金属行为的宽松合金，确定了sn成分$ x $的函数，并且通过将垂直于[001]生长方向垂直于GE，GE，GE，Teeluride（Znte），Tellurede（Znte），或Cadmium Tellures（Cadmium Tellate）（cadmium Tellate）（CDTETTE）的SUPCEL晶格常数（CDTETTE）固定在垂直于[001]生长方向上。发现与放松的GE $ _ {1-x} $ _ {1-x} $ sn $ _ {x} $相同隙相同的GAP相同的GE $ _ {1-x} $ _ {1-x} $ _ {1-x} $ _ {1-X} $ _ {1-X} $ _ {1％的直接频带隙提高了约5％所需的SN组合物所需的SN组成。另一方面，压缩应变对$γ$的合金带隙的影响相对较小。使用DFT计算出的合金晶格和弹性常数，估计了$ x $ $ x $ thin薄膜的GE $ _ {1-X} $ sn $ _ {1-x}的临界厚度，并估算了基板晶格常数，并根据超级细胞DFT计算进行了验证。该分析正确预测了SN组成范围，在该范围内，它对GE $ _ {1-X} $ sn $ _ {x} $/ge变得无定形的SN组成范围。研究化学计量和应变的影响是降低倒置（``负''）$γ_{7}^{ - } $ - $γ_{8}^{+} $ band Gap的幅度的影响。根据我们的发现，提出了通过应变和量子限制在ge $ _ {1-x} $ sn $ _ {x} $纳米结构中通过应变和量子限制进行工程的策略。
We calculate the electronic structure of germanium-tin (Ge$_{1-x}$Sn$_{x}$) binary alloys for $0 \leq x \leq 1$ using density functional theory (DFT). Relaxed alloys with semiconducting or semimetallic behaviour as a function of Sn composition $x$ are identified, and the impact of epitaxial strain is included by constraining supercell lattice constants perpendicular to the [001] growth direction to the lattice constants of Ge, zinc telluride (ZnTe), or cadmium telluride (CdTe) substrates. It is found that application of 1% tensile strain reduces the Sn composition required to bring the (positive) direct band gap to zero by approximately 5% compared to a relaxed Ge$_{1-x}$Sn$_{x}$ alloy having the same gap at $Γ$. On the other hand, compressive strain has comparatively less impact on the alloy band gap at $Γ$. Using DFT calculated alloy lattice and elastic constants, the critical thickness for Ge$_{1-x}$Sn$_{x}$ thin films as a function of $x$ and substrate lattice constant is estimated, and validated against supercell DFT calculations. The analysis correctly predicts the Sn composition range at which it becomes energetically favourable for Ge$_{1-x}$Sn$_{x}$/Ge to become amorphous. The influence of stoichiometry and strain is examined in relation to reducing the magnitude of the inverted (``negative'') $Γ_{7}^{-}$-$Γ_{8}^{+}$ band gap, which is characteristic of semimetallic alloy electronic structure. Based on our findings, strategies for engineering the semimetal-to-semiconductor transition via strain and quantum confinement in Ge$_{1-x}$Sn$_{x}$ nanostructures are proposed.
