The difference in the free energy of the barrier is even more pronounced than the difference in net free energy. As the main contribution to the energy of the barrier is the desorption of a CH3 group from the surface, this is also a clear indicator that InN binds CH3 harder compared to GaN. The difference in the barrier is between 86-108 kJ mol -1 at ALD temperature. Comparing rate constants of adsorption obtained from these barriers by transition state theory, Table , indicates that the chemisorption of NH3 is many orders of magnitudes slower on InN compared to GaN, with the ration of rate constant for adsorption on InN divided by the constant for adsorption on GaN ranging from 1.0 × 10 -9 at 500 K to 9.2 × 10 -8 at 800 K. Furthermore, the rate constant for adsorption on InN at 800 K is of the same magnitude as the rate constant for adsorption on GaN at STP, which is much lower than the temperatures used in thermal GaN ALD. For an ALD process of InN with thermal NH3 to work in a similar time frame as for GaN, either the temperature of the process must be increased, which is hindered by the thermal instability, or the NH3 pressure must be increased significantly, well outside the possible working pressures for ALD.