Effect of the substrate and alignment on the strain distribution in periodic QD structures

• Published in: Journal of alloys and compounds 2009-08, Vol.483 (1), p.306-308
• Main Authors: Skoulidis, N., Polatoglou, H.M.
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Crystal structure; Exact sciences and technology; Low-dimensional structures (superlattices, quantum well structures, multilayers): structure, and nonelectronic properties; Nitride materials; Physics; Quantum dots; Semiconductors; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2008.07.174

In this study we have investigated theoretically the strain fields of cubic GaN quantum dot superlattices embedded in zinc-blend AlN induced by the relative position of quantum dots and by the substrate composition. We have produced atomistic structures that model nanostructures grown along [0 0 1] direction on a GaN/AlN alloy substrate. First we found that it is energetically favorable for the quantum dots to be vertically aligned in consecutive dot layers. Also there is a similar but less intense preference for the dots of the same layer to form a square two-dimensional lattice. These two results are in accordance with experimental data for GaN/AlN quantum dots but also with different compounds. We found that due to the inclusion of QDs, the AlN matrix expands but to a lesser degree compared to a random alloy with the same atomic composition. With the energetically favorable quantum dots arrangement, an effective wire-like strained AlN structure is created, parallel to the growing axis, which might have influence in the electronic structure and optical properties of the quantum dots array. This structure depends on the substrate composition and disappears when the content of GaN in the substrate is increased.