MBE growth of Ga droplets with the size of wide distribution via an in-situ laser irradiation

Droplet epitaxy is a very powerful technology for the fabrication of semiconductor quantum optoelectronic devices due to its offering all-preparation of quantum dots, nanowires and nanorings. As is known, the size control of the droplets is a key issue for the droplet epitaxy. Usually, the droplet size is adjusted by the growth temperature and growth rate based on the well-known MBE method, but it is still quite limited. In this work, we attempted to use an in situ laser irradiation to modify the Ga droplet size during the MBE growth. Two groups of samples were prepared: for all the samples, after the growth of a 300nm GaAs buffer layer on GaAs substrate, the total following deposition amount of Ga is 8ML with a single in-situ shot of laser irradiation. In contrast, for group A, the exposure was performed when the 8ML Ga deposition was completely finished, while for group B, the exposure was inserted in the middle of the deposition, i.e., when it reached 4ML. We carefully compared the effect of the insertion position of the exposure on the obtained droplet morphology with different pulse energies. The results show the droplet size can be strongly adjusted via the in-situ laser irradiation especially when it is inserted in the middle of the droplet growth. Finally, droplets have specific heights and widths with an extremely wide distribution ranging from 0.7nm to 97.3nm and 21.6nm to 396.5nm, respectively, are successfully realized.