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HL: Fachverband Halbleiterphysik
HL 22: Heterostructures, Interfaces and Surfaces
HL 22.3: Vortrag
Mittwoch, 7. September 2022, 15:30–15:45, H33
Excitonic fine structure of epitaxial Cd(Se,Te) on ZnTe type-II quantum dots — •Petr Klenovsky1,2, Piotr Baranowski3, and Piotr Wojnar3 — 1Department of Condensed Matter Physics, Faculty of Science, Masaryk University, Kotlářská 267/2, 61137 Brno, Czech Republic — 2Czech Metrology Institute, Okružní 31, 63800 Brno, Czech Republic — 3Institute of Physics, Polish Academy of Sciences, Al Lotników 32/46, PL-02-668 Warsaw, Poland
The structure of the ground state exciton of Cd(Se,Te) quantum dots embedded in ZnTe matrix is studied experimentally using photoluminescence spectroscopy and theoretically using k·p and configuration interaction methods. The experiments reveal a considerable reduction of fine-structure splitting energy of the exciton with increase of Se content in the dots. That effect is interpreted by theoretical calculations to originate due to the transition from spatially direct (type-I) to indirect (type-II) transition between electrons and holes in the dot induced by increase of Se. The trends predicted by the theory match those of the experimental results very well.
The theory identifies that the main mechanism causing elevated fine-structure energy in particular in type-I dots is due to the multipole expansion of the exchange interaction. Moreover, the theory reveals that for Se contents in the dot >0.3, there exist also a peculiar type of confinement showing signatures of both type I and type II and which exhibits extraordinary properties, such as almost purely light hole character of exciton and toroidal shape of hole states.