GaSb quantum dot morphology for different growth temperatures and the dissolution effect of the GaAs capping layer

We compare the characteristics of GaSb quantum dots (QDs) grown by molecular beam epitaxy on GaAs at temperatures from 400 to 490 °C. The dot morphology, in terms of size, shape and density, as determined by atomic force microscopy (AFM) on uncapped QDs, was found to be highly sensitive to the growth temperature. Photoluminescence (PL) spectra of capped QDs are also strongly dependent on growth temperature, but for samples with the highest dot density, where the QD luminescence would be expected to be the most intense, it is absent. We attribute this to dissolution of the dots by the capping layer. This explanation is confirmed by AFM of a sample that is thinly capped at 490 °C. Deposition of the capping layer at low temperature resolves this problem, resulting in strong QD PL from a sample with a high dot density.