论文标题
从头开始研究新颖亚稳态BC8/ST12 SI $ _x $ ge $ _ {1-x} $合金
Ab initio study of band gap properties in novel metastable BC8/ST12 Si$_x$Ge$_{1-x}$ alloys
论文作者
论文摘要
立方$ ia \ bar {3} $（BC8）和四方$ P4_32_12 $（ST12）SI和GE的高压修饰是用于光电，热电学或等离子设备中应用的有吸引力的候选者。 Si $ _x $ ge $ _ {1-x} $合金在BC8/ST12修改中可以帮助克服纯相位的间接和窄带间隙，并为特定用例启用量身定制。在高压合成后释放后，在实验上发现这种合金在环境条件下是稳定的，但是它们的基本特性尚不清楚。在这项工作中，我们基于密度功能理论（DFT）采用{\ it i ab intib}计算来研究这些化合物的电子特性作为组成$ x $的函数。我们通过构建特殊的准随机结构（SQ）并将其带状结构展开到相应的原始细胞来获得中间合金的有效带结构。此外，我们表明，可以将ST12 GE End-Member的间接频带间隙调谐为$ x_ \ text {si} \大约0.16 $。最后，我们的研究还表明，另一方面，BC8修饰对组成变化不敏感，并且仅在纯SI的情况下才是狭窄的直接带隙半导体。
The cubic $Ia\bar{3}$ (BC8) and tetragonal $P4_32_12$ (ST12) high pressure modifications of Si and Ge are attractive candidates for applications in optoelectronic, thermoelectric or plasmonic devices. Si$_x$Ge$_{1-x}$ alloys in BC8/ST12 modifications could help overcome the indirect and narrow band gaps of the pure phases and enable tailoring for specific use-cases. Such alloys have experimentally been found to be stable at ambient conditions after release from high pressure synthesis, however their fundamental properties are not known. In this work, we employ {\it ab initio} calculations based on density functional theory (DFT) to investigate the electronic properties of these compounds as a function of composition $x$. We obtain the effective band structures of intermediate alloys by constructing special quasi random structures (SQS) and unfolding their band structure to the corresponding primitive cell. Furthermore, we show that the indirect band gap of the ST12 Ge end-member can be tuned to become direct at $x_\text{Si} \approx 0.16$. Finally, our investigations also demonstrate that the BC8 modification, on the other hand, is insensitive to compositional changes and is a narrow direct band gap semiconductor only in the case of pure Si.
