Growth of InAs quantum dots on the modified GaAs surface by using in-situ multi-pulsed laser shooting

In this work, we subjected the GaAs substrate to in-situ irradiation by 10 laser pulses with 30 second interruption among each pulse at a temperature of 500℃ without As flux. Then the substrate was annealed at the same temperature for 5 minutes under As flux. We have respectively prepared a series of samples corresponding to different pulse energies (1mJ-8mJ). At the very low energy stage (1-2mJ), oval islands elongated along [-110] can be observed on the surface. At the medium energy stage (2-4mJ), the oval islands will become larger and meanwhile some very narrow nano grooves (elongated along [110]) will appear at the center of the island. At the high energy stage (4-8mJ), the islands will become larger and the grooves will widen into nano holes. The whole structure almost looks like a nano ring with a nano hole at the center. Then, we conducted a study of InAs quantum dot growth on these obtained nano structures. The results show all the InAs quantum dots strictly grow surrounding the oval islands or in the nano holes after the deposition of 2.2ML InAs at 500℃. So these structures can effectively serve as the preferential nucleation sites for quantum dots.