The band structure and optical gain of a new IV-group alloy GePb: A first-principles calculation
The band structure and optical gain of a new IV-group alloy GePb: A first-principles calculation
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新型IV族合金GePb的能带结构和光学增益：第一性原理计算
DOI：
10.1016/j.jallcom.2017.01.195
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发表时间：
2017
影响因子：
6.2
通讯作者：
Yang Hong
中科院分区：
文献类型：
--
作者：
Huang Wenqi;Cheng Buwen;Xue Chunlai;Yang Hong
一种新型硅基材料GePb被预测具有直接带隙，引起了硅基光源制造领域的广泛关注。为了精确地研究其能带结构和光照效率，采用了结合DFT + U方法和超级单体模型的第一次主要计算。对于未应变的GePb，从间接带隙到直接带隙，计算出的Pb浓度交叉值为3.4%，远低于GeSn。同时，它的最大光学增益远高于GeSn，这意味着GePb可能是制造硅基激光器的更好选择。为了减少直接带隙GePb对Pb的需求，计算了合金化Pb和施加（111）双轴应变作用下的能带结构和光增益。结果表明，在1.13%的压缩应变条件下，GePb对Pb的需用量可进一步降低至2.1%，适度的应变强度更有利于提高其光学增益。这意味着这两种方法的结合可以更好地调节GePb的能带结构和光学增益。针对在（111）Ge缓冲层上生长的压缩应变GePb，计算了全应变GePb的能带结构和光增益。计算得到Pb的交叉值为2.7%，GePb的光学增益随Pb浓度的增加而增加。这意味着在（111）Ge缓冲液上生长GePb不仅可以减少其对Pb的需求，还可以提高其照明效率。
A new Si-based material GePb which has been predicted to possess a direct-bandgap attracts much attention in the field of fabricating Si-based light source recently. To precisely investigate its band structure and lighting efficiency, the first principal calculations combined with DFT + U method and supercell models are employed. For unstrained GePb, the calculated crossover value of Pb concentration changing it from an indirect to a direct bandgap is evaluated to 3.4%, which is much lower than that of GeSn. Meanwhile, its maximum optical gain is much higher than that of GeSn, which means GePb could be a better choice for fabricating Si-based laser. To reduce the direct-bandgap GePb's need for Pb, its band structures and optical gains under the effects of alloying Pb and applying (111)-biaxial strains are calculated. The results indicate that GePb's need for Pb can be further reduced to 2.1% with the aid of 1.13% compressive strain, and the moderate strain strength is more beneficial to improve its optical gain. This means the combination of these two methods could be a better way to tune the band structure and optical gain of GePb. Aiming to the compressively strained GePb grown on (111) Ge buffer, the band structures and optical gains of fully strained GePb are calculated. The calculated crossover value of Pb is 2.7%, and the optical gain of GePb increases as Pb concentration increases. This means growing GePb on (111) Ge buffer not only can reduce its need for Pb, but also can improve its lighting efficiency.