Electronic structure and stability of quaternary chalcogenide semiconductors derived from cation cross-substitution of II-VI and I-III-VI2 compounds
Electronic structure and stability of quaternary chalcogenide semiconductors derived from cation cross-substitution of II-VI and I-III-VI2 compounds
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DOI：
10.1103/physrevb.79.165211
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发表时间：
2009-04-01
影响因子：
3.7
通讯作者：
Wei, Su-Huai
中科院分区：
文献类型：
--
作者：
Chen, Shiyou;Gong, X. G.;Wei, Su-Huai
用第一性原理电子结构计算方法系统地研究了闪锌矿硫系半导体中从二元到三元再到四元化合物的顺序阳离子交叉取代。发现了三元和两类四元硫系化合物的几个普遍趋势，例如，与共排阳离子取代的亚稳态结构相比，最低能量结构总是具有更大的晶格常数a，更小的四方形变参数Eta=c/2a，价带顶部的负晶场分裂，以及更大的带隙。从能带偏移量和能带特征分解的角度分析了阳离子取代过程中的能带结构变化，结果表明，虽然带隙从II-VI降低到I-III-VI2的三元是由于价带中的p-d排斥，但从I-III-VI2到I-2-II-IV-VI4四元硫族化合物的带隙减小是由于第四族阳离子位置上的波函数局域化导致导带的下移。我们认为，共排阳离子I-2-II-IV-VI4在方锡矿结构中更稳定，而文献中广泛报道的实验样品的锡矿结构很可能是由于方铅矿相I-II(001)层的部分无序所致。
Sequential cation cross-substitution in zinc-blende chalcogenide semiconductors, from binary to ternary to quaternary compounds, is systematically studied using first-principles electronic structure calculations. Several universal trends are found for the ternary and two classes of quaternary chalcogenides, for example, the lowest-energy structure always has larger lattice constant a, smaller tetragonal distortion parameter eta=c/2a, negative crystal-field splitting at the top of the valence band, and larger band gap compared to the metastable structures for common-row cation substitution. The band structure changes in the cation substitution are analyzed in terms of the band offsets and band character decomposition, showing that although the band gap decreases from binary II-VI to ternary I-III-VI2 are mostly due to the p-d repulsion in the valence band, the decreases from ternary I-III-VI2 to quaternary I-2-II-IV-VI4 chalcogenides are due to the downshift in the conduction band caused by the wave-function localization on the group IV cation site. We propose that common-row-cation I-2-II-IV-VI4 compounds are more stable in the kesterite structure, whereas the widely assumed stannite structure reported in the literature for experimental samples is most likely due to partial disorder in the I-II (001) layer of the kesterite phase.