Tit Nacir, Obaidat Ihab M, Alawadhi Hussain
Department of Physics, UAE University, PO Box 17551, Al-Ain, United Arab Emirates.
J Phys Condens Matter. 2009 Feb 18;21(7):075802. doi: 10.1088/0953-8984/21/7/075802. Epub 2009 Jan 29.
We present an investigation into the existence and origins of bandgap bowing in compound-semiconductor common-cation ternary alloys. As examples, we consider CdSe(x)Te(1-x) and ZnSe(1-x)Te(x) alloys. A calculation, based on the sp(3)s(*) tight-binding method including spin-orbit coupling within the framework of the virtual crystal approximation, is employed to determine the bandgap energy, local density of states and atomic charge states versus composition and valence-band offset. The results show that (i) in the valence band, the top states are mainly contributed by Te atoms. The degree of ionicity of all atoms is found to vary linearly with mole fraction x. (ii) There is a strong competition between the anions (Se and Te) in trapping/losing charges and this competition is the main reason for the bandgap bowing character. (iii) There is a reasonable agreement between the calculated results and the available photoluminescence data. (iv) The bowing parameter is found to increase with increasing valence-band offset and increasing lattice mismatch.
我们对化合物半导体共阳离子三元合金中带隙弯曲的存在及其起源进行了研究。作为示例，我们考虑了CdSe(x)Te(1-x)和ZnSe(1-x)Te(x)合金。采用基于sp(3)s(*)紧束缚方法并在虚拟晶体近似框架内包含自旋轨道耦合的计算，来确定带隙能量、局域态密度以及原子电荷态随成分和价带偏移的变化。结果表明：(i) 在价带中，顶部态主要由Te原子贡献。发现所有原子的离子性程度随摩尔分数x线性变化。(ii) 阴离子（Se和Te）在俘获/失去电荷方面存在强烈竞争，这种竞争是带隙弯曲特性的主要原因。(iii) 计算结果与现有的光致发光数据之间存在合理的一致性。(iv) 发现弯曲参数随价带偏移的增加和晶格失配的增加而增大。
