9.
Microphotoluminescence from GaN/AlN quantum dots grown by molecular beam epitaxy on sapphire substrates along the (0001) axis
has been studied. To produce quantum dots of different average sizes and densities, the nominal amount of deposited GaN has
been varied from 1 to 4 ML. The density of the quantum dots was about 10
11 cm
−2, which corresponded to about 10
3 quantum dots excited in the experiments. The photo-luminescence from the quantum dots was linearly polarized and the maximum
polarization degree (15%) has been observed for the sample with the lowest amount of deposited GaN. The photoluminescence
intensity from this sample under continuous laser excitation decreased by more than two orders of magnitude for about 30 min
and then stabilized. The photoluminescence intensity from other samples under continuous excitation remained constant. We
suggest that a rather high polarization degree is caused by anisotropy in the strain and shape of the quantum dots formed
near the dislocations, which also act as the centers of nonradiative recombination.
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