Pushing the Band Gap Envelope of Quasi-Type II Heterostructures to Blue: ZnSe/ZnSe<SUB>1-X</SUB>Te<SUB>X</SUB>/ZnSe Spherical Quantum Wells
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초록
내용
ZnSe1-XTeX is promising Cd-free quantum dots (QDs) because of its wide band gap tunability. However, there are major obstacles on achieving highly luminescent ZnSe1-XTeX QDs. First, high reactivity of tellurium precursor and large lattice mismatch between ZnSe and ZnTe (7.7 %) induce inhomogeneous nucleation of ZnSe and ZnTe. Second, undisclosed band position of ZnSe1-XTeX hinders designing sophisticate core/shell heterostructures. Herein, we propose highly luminescent ZnSe/ZnSe1-XTeX/ZnSe spherical quantum wells (SQWs) as a new class of Cd-free quasi-type Ⅱ heterostructure. By introducing SQW structure, we alleviate lattice mismatch and interfacial defect effectively and accomplish high PL QY (＞ 90%) even at high X (0.5). Additionally, spectroscopic analysis clarifies quasi-type Ⅱ band alignment of ZnSe/ZnSe1-XTeX/ZnSe QDs. Based on these results, we control two factor, ZnSe shell thickness (dimension) and X (composition), to tune band gap widely with high PL QY.