In situ spectroscopic ellipsometry kinetic characterization is used to monitor the behavior of Ga atoms during and after Ga flux impingement upon a (0001) GaN surface at various temperatures in the range of 680-750 °C. The observed saturation of the pseudodielectric function verifies the existence of a critical thickness for the Ga wetting layer, while the observed desorption delay after the Ga flux is terminated indicates the presence of two Ga phases, one acting as a Ga reservoir to compensate the desorption of the wetting layer until the other phase is depleted. © 2006 American Institute of Physics.