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The optical properties of In0:5Ga0:5As-GaAs single-layer quantum dots (SL-QDs) and three vertically stacked double-layer quantum dots (DL-QDs) with di erent spacer thicknesses, grown by solid-source molecular beam epitaxy (MBE) in Stranski-Krastonow (S-K) growth mode, are investigated by micro-photoluminescence (-PL) spectroscopy. Interestingly, -PL spectra of all DL-QDs are observed at energies lower by approximately 40 meV, compared with those of SL-QDs, indicating the e ective coupling of DL-QDs, along with multiple sub-peaks on the right shoulder of the luminescence center. A reduction in overall energies of the quantum dot (QD) in terms of electronic coupling, and the creation of multiple energy states in terms of mutual interactions among the DL-QDs of di erent sizes and shapes, are considered to be possible reasons for this phenomenon. The excitation-power-dependent -PL spectra also show state- lling e ects in the lowest energy levels of the DL-QDs.


The optical properties of In0:5Ga0:5As-GaAs single-layer quantum dots (SL-QDs) and three vertically stacked double-layer quantum dots (DL-QDs) with di erent spacer thicknesses, grown by solid-source molecular beam epitaxy (MBE) in Stranski-Krastonow (S-K) growth mode, are investigated by micro-photoluminescence (-PL) spectroscopy. Interestingly, -PL spectra of all DL-QDs are observed at energies lower by approximately 40 meV, compared with those of SL-QDs, indicating the e ective coupling of DL-QDs, along with multiple sub-peaks on the right shoulder of the luminescence center. A reduction in overall energies of the quantum dot (QD) in terms of electronic coupling, and the creation of multiple energy states in terms of mutual interactions among the DL-QDs of di erent sizes and shapes, are considered to be possible reasons for this phenomenon. The excitation-power-dependent -PL spectra also show state- lling e ects in the lowest energy levels of the DL-QDs.