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Multilayer, vertically coupled, quantum dot structures are investigated using layers composed of InAs islands grown by molecular beam epitaxy in the Stranski-Krastanov growth mode. Single, 2, 5, and 10 InAs island layers are investigated in which the 40 high InAs islands are separated by 56 GaAs spacer layers. The InAs islands are vertically aligned in columns and are pseudomorphic. Between 1 and 10 layers of islands, 8 K photoluminescence shows a 25% reduction in PL linewidth, and a peak shift of 92 meV to lower energy, while transmission electron and atomic force microscopy show the island size in different layers remains constant. These effects are attributed to electronic coupling between islands in the columns, and a simple coupling model is used to simultaneously fit the spectral peak position shift and the linewidth changes.
Solomon et al. (Mon,) studied this question.