掺氦稳定的直接带隙硅化物
Helium Incorporation Stabilized Direct-gap Silicides
摘要：
由于直接带隙硅基半导体在许多技术相关领域中的潜在应用，因此对直接带隙硅基半导体的研究具有极大的兴趣。这项工作探讨了作为一种可能的路线，以形成一个直接的带隙在Si中的他的掺入。结构预测和第一性原理计算表明He与Si在高压下反应生成稳定的化合物Si 2 He和Si 3 He。这两种化合物都具有由充满He客体原子的通道状Si主体框架组成的主客体结构。两种化合物中的Si骨架在去除He后可以保持到常压，形成两种纯的Si同素异形体。两种Si-He化合物和两种Si同素异形体都表现出0.84-1.34 eV的直接或准直接带隙，接近太阳能电池应用的最佳值（~1.3 eV）。分析表明，具有电偶极跃迁允许带隙的Si 2 He具有比金刚石立方Si更高的吸收容量，是一种很有前途的薄膜太阳能电池候选材料。
英文摘要：
The search of direct-gap Si-based semiconductors is of great interest due to the potential application in many technologically relevant fields. This work examines the incorporation of He as a possible route to form a direct band gap in Si. Structure predictions and first-principles calculations have shown that He reacts with Si at high pressure, to form the stable compounds Si2He and Si3He. Both compounds have host-guest structures consisting of a channel-like Si host framework filled with He guest atoms. The Si frameworks in two compounds could be persisted to ambient pressure after removal of He, forming two pure Si allotropes. Both Si-He compounds and both Si allotropes exhibit direct or quasi-direct band gaps of 0.84-1.34 eV, close to the optimal value (~1.3 eV) for solar cell applications. Analysis shows that Si2He with an electric-dipole-transition allowed band gap possesses higher absorption capacity than diamond cubic Si, which makes it to be a promising candidate material for thin-film solar cell.
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