Evidence of 2D-3D transition during the first stages of GaN growth on AlN
F. Widmann, B. Daudin, G. Feuillet, Y. Samson, M. Arlery, J. L. Rouviere
CEA/Grenoble, Département de Recherche Fondamentale sur la Matière Condensée/SP2M
This article was received on July 8, 1997 and
accepted on August 21, 1997. Abstract
In order to identify the strain relaxation mechanism,
Molecular Beam Epitaxy of wurtzite GaN on AlN was monitored in situ using
Reflection High Energy Electron Diffraction (RHEED). In the substrate
temperature range between 620°C and 720°C, a Stransky-Krastanov
(SK) transition was evidenced, resulting in a 2D-3D transition after completion
of 2 monolayers, with subsequent coalescence of 3D islands, eventually
resulting in a smooth surface. Quantitative analysis of the RHEED pattern
allowed us to determine that island formation is associated with elastic
relaxation. After island coalescence, a progressive plastic relaxation is
observed. The size and density of 3D islands was varied as a function of the
growth parameters. AFM experiments revealed that the size of the GaN islands,
about 8 nm large and 2 nm high, was small enough to expect quantum effects. It
was found that capping of the islands by AlN resulted in a smooth surface after
deposition of a few monolayers allowing us to grow a "superlattice"
of islands by periodically repeating the process.
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Cite this article as: MRS Internet J. Nitride Semicond. Res. 2, 20(1997).
last updated October 15, 1997 4:01:55 PM.© 1997 The Materials Research Society
