GaN quantum dots grown on Al_xGa_(1-x)N layer by plasma-assisted molecular beam epitaxy

摘要

We report on the growth of GaN quantum dots on an Al_xGa_(1-x)N layer. Taking advantage of the delayed strain relaxation of AlGaN on an AlN template, we were able to grow GaN quantum dots on an AlGaN layer with Al content as low as 34%. Real-time monitoring of the variations of the in-plane lattice parameter revealed that the growth of the self-organized GaN quantum dots depended not only on the in-plane lattice mismatch but also on the chemical composition of the underlying layer. The morphological properties of the GaN quantum dots were studied by atomic force microscopy. The size distribution of the quantum dots varied from bimodal to monomodal at 80% Al content. Monomodal quantum dots decreased the aspect ratio when the Al content of the AlGaN layer decreased, which is consistent with a reduced elastic relaxation compensated for by a decrease of interfacial energy.