We present a theoretical analysis of vertical versus radial growth of MP nanowires obtained by selective area metalorganic molecular beam epitaxy at temperatures from 400 to 480 degrees C. It is shown that the nanowire formation is controlled by surface diffusion of indium adatoms whose concentration On the sidewalls determines the local radial growth rate. Two models for the radial growth rate are considered, with linear (step flow) and exponential (two-dimensional nucleation) dependences on the adatom concentration. The linear model reproduces fairly well the vertical elongation rate and the observed shapes of the upper nanowire parts, while the non-linear shapes at the nanowire bottom are described ! correctly only within the exponential model. We estimate the effective migration lengths of indium, which are of the order of several hundreds of nanometers between 400 and 450 degrees C. The migration length increases up to 2200 nm at 480 degrees C so that radial growth is completely suppressed at this high growth temperature. (C) 2014 Elsevier B.V. All rights reserved.