Insights into the growth mechanism of In xGa 1−xN epitaxial nanostructures formed using a silane predose

Abstract

In x Ga 1− x N/GaN quantum dot (QD) arrays with high spatial densities have the potential to improve the performance of GaN-based optoelectronic devices. The growth of such QD arrays may be achieved in metal–organic vapour phase epitaxy by pre-dosing the GaN surface with a silicon-bearing precursor. Here, we investigate the mechanism of QD formation in this case, and suggest that for short SiH 4 predoses, the variation of island density with predose duration, and the merging of the observed islands with increasing In x Ga 1− x N growth time, indicate that the SiH 4 is roughening the GaN surface, increasing the number of available nucleation sites, and leading to a change in growth mode. For longer SiH 4 predoses, a different mechanism appears to operate. However, we find no evidence for the presence of an SiN x nanomask, but instead note that the observed islands have a distinctive and consistent shape, indicating the influence of strain and surface energy contributions on the growth mode.