Indirect band gaps in quantum dots made from direct-gap bulk materials
Indirect band gaps in quantum dots made from direct-gap bulk materials
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由直接带隙块体材料制成的量子点中的间接带隙
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
A. Zunger
中科院分区：
文献类型：
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作者：
A. Williamson;A. Franceschetti;H. Fu;L. Wang;A. Zunger
摘要讨论了独立半导体量子点和嵌入式半导体量子点直接或间接产生带隙的条件。半导体量子点分为三类；(i)独立点，（ii）嵌入直接间隙矩阵的点，以及（iii）嵌入间接间隙矩阵的点。对于每一类，首先讨论定性预测，然后是最近的实验结果和最先进的伪势计算。我们表明：InP， InAs和CdSe的独立点将在所有尺寸下保持直接，而GaAs和InSb制成的点将在临界尺寸以下间接转变。嵌入在直接间隙矩阵材料中的点要么保持直接（零压力下的InAs/GaAs），要么在临界尺寸（InSb/InP）下变为间接。嵌入在间接间隙矩阵材料中的点对于足够小的点（GaAs/AlAs和InP/ gap量子阱）将表现出向间接间隙的过渡，或者将始终是间接的（InP/ gap点，压力高于43 k bar的InAs/GaAs和GeSi/Si点）。
AbstractThe conditions under which the band gaps of free standing and embedded semiconductor quantum dots are direct or indirect are discussed. Semiconductor quantum dots are classified into three categories; (i) free standing dots, (ii) dots embedded in a direct gap matrix, and (iii) dots embedded in an indirect gap matrix. For each category, qualitative predictions are first discussed, followed by the results of both recent experiments and state of the art pseudopotential calculations. We show that:Free standing dots of InP, InAs, and CdSe will remain direct for all sizes, while dots made of GaAs and InSb will turn indirect below a critical size.Dots embedded within a direct gap matrix material will either stay direct (InAs/GaAs at zero pressure) or will become indirect at a critical size (InSb/InP).Dots embedded within an indirect gap matrix material will exhibit a transition to indirect gap for sufficiently small dots (GaAs/AlAs and InP/GaP quantum well) or will be always indirect (InP/GaP dots, InAs/GaAs above 43 k bar pressure and GeSi/Si dots).
In indirect nanostructures, charge separation can occur with electrons and holes localized on different materials (flat InP/GaP quantum well) or with electrons and holes localized in different layers of the same material (concentric cylindrical GaAs/AlAs layers).