Spectroscopic ellipsometry installed on a GEN-II plasma assisted molecular beam epitaxy machine has been shown to be art effective in situ real time tool for monitoring the kinetics of gallium adlayer adsorption/desorption on the GaN surface. In this work, the authors present data on the study of Ga adsorption/desorption on polar c-plane GaN (0001) and nonpolar m-plane GaN (1 - 100) surfaces for Ga beam equivalent pressures in the range of 8.96X 10(-8)-1.86x 10(-7) Torr, Ga pulses in the range of 5-360 s, and for substrate temperatures between 650 and 750 degrees C. (c) 2007 American Vacuum Society.