We investigate the axial and radial growth of GaN nanowires upon a variation of the Ga flux during molecular beam epitaxial growth. An increase in the Ga flux promotes radial growth without affecting the axial growth rate. In contrast, a decrease in the Ga flux reduces the axial growth rate without any change in the radius. These results are explained by a kinetic growth model that accounts for both the diffusion of Ga adatoms along the side facets towards the nanowire tip and the finite amount of active N available for the growth. The model explains the formation of a new equilibrium nanowire radius after increasing the Ga flux and provides an explanation for two well known but so far not understood experimental facts: the necessity of effectively N-rich conditions for the spontaneous growth of GaN nanowires and the increase in nanowire radius with increasing III/V flux ratios.
@article{arxiv.2402.01756,
title = {Self-regulated radius of spontaneously formed GaN nanowires in molecular beam epitaxy},
author = {Sergio Fernández-Garrido and Vladimir M. Kaganer and Karl K. Sabelfeld and Tobias Gotschke and Javier Grandal and Enrique Calleja and Lutz Geelhaar and Oliver Brandt},
journal= {arXiv preprint arXiv:2402.01756},
year = {2024}
}