Size and shape tunability of self-assembled InAs/GaAs nanostructures through the capping rate

• Published in: Applied surface science 2018-06, Vol.444, p.260-266
• Main Authors: Utrilla, Antonio D., Grossi, Davide F., Reyes, Daniel F., Gonzalo, Alicia, Braza, Verónica, Ben, Teresa, González, David, Guzman, Alvaro, Hierro, Adrian, Koenraad, Paul M., Ulloa, Jose M.
• Format: Article
• Language: English
• Subjects: Capping rate; Dissolution process; Molecular beam epitaxy; Quantum dot; Quantum ring; Wetting layer
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2018.03.098

InAs/GaAs nanostructure tunability through the capping rate: from quantum rings to completely preserved pyramidal quantum dots. [Display omitted] •Control over the thermodynamic equilibrium structure through the capping rate.•InAs/GaAs quantum dot size and geometry preservation at high capping rates.•Tunability of the InAs/GaAs quantum dot ground state through the capping rate.•Tunability of the wetting layer thickness through the capping rate. The practical realization of epitaxial quantum dot (QD) nanocrystals led before long to impressive experimental advances in optoelectronic devices, as well as to the emergence of new technological fields. However, the necessary capping process is well-known to hinder a precise control of the QD morphology and therefore of the possible electronic structure required for certain applications. A straightforward approach is shown to tune the structural and optical properties of InAs/GaAs QDs without the need for any capping material different from GaAs or annealing process. The mere adjust of the capping rate allows controlling kinetically the QD dissolution process induced by the surface In-Ga intermixing taking place during overgrowth, determining the final metastable structure. While low capping rates make QDs evolve into more thermodynamically favorable quantum ring structures, increasing capping rates help preserve the QD height and shape, simultaneously improving the luminescence properties. Indeed, a linear relationship between capping rate and QD height is found, resulting in a complete preservation of the original QD geometry for rates above ∼2.0 ML s−1. In addition, the inhibition of In diffusion from the QDs top to the areas in between them yields thinner WLs, what could improve the performance of several QD-based optoelectronic devices.