Predictive model for the temporal evolution of the shape of GaAs nanowires

We study the evolution of the shape (degree and sign of tapering) of Ga-assisted GaAs nanowires in molecular beam epitaxy. Here, we extend our previously published model for the diameter evolution in order to predict the nanowire shape over a large range of growth parameters. We use experimental data to connect parameters of different parts of the model. The predictive model reveals that an untapered nanowire shape can only be obtained for certain sets of diameter and length. The diffusion length of Ga atoms is found to be a determining parameter and by varying it the range of obtainable nanowire shapes may be modified.