Thuy et al. have published a paper on quantum dots of InP/ZnS alloy. For my application I would like to know if this alloy is a direct bandgap semiconductor.
Article Comparative photoluminescence study of close-packed and coll...
no ,you must calculate the band structure , or you can found the answer in the literature
Just note InP is a III-V compound, and ZnS is a II-V compound, thus they can hardly form alloy in normal conditions. What the paper claimed is, I believe, the formation of `alloy-like' nanostructures, whose optical properties are similar with InP small dots capped by ZnS. Consequently, I think we can see their sample as a direct-gap material.
Ambiguity in the question makes it difficult to answer. I am assuming the question to relate to InP/ZnS alloy.
Although, InP is a III-V and ZnS a II-VI compound, they certainly can be mixed (or alloyed or formed solid solution) depending upon how well they satisfy the mixing criteria: identical crystal structure, nearly same lattice constant, etc. InP has Zinc Blende crystal structure; ZnS can also be obtained with the Zinc Blende crystal structure. The lattice constant of InP is 0.567 nm, whereas that of ZnS is 0.542 nm; the difference is not too large. It is not necessary that the InP/ZnS alloy will have a direct band-gap at all mixing ratios. In general, for a semiconductor alloy, the direct band-gap and the indirect band-gap will change with the mixing ratio in a nearly linear fashion; if these lines have significantly different slopes and intersect, then, the alloy will change from a direct to an indirect band-gap.
Thanks for all the comments and suggestions. I agree with Dr. Kuroda that the structure described by Thuy et al can not be characterized as an alloy in the classical sense.
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