Both first-principles calculations and kinetic Monte Carlo simulations were performed in order to study the diffusion and thermal stability of H in ZnO. The migration energy of substitutional hydrogen, HO, was 1.7eV; much higher than the value of 0.4 to 0.5eV for interstitial hydrogen, Hi. Using as input the calculated energy barriers for H diffusion, kinetic Monte Carlo simulations showed that while Hi diffused out at low temperatures, the thermal stability of HO was maintained up to 475C, in good agreement with annealing data. The calculations suggested that injected H from air turned into HO, causing n-type conductivity.

Diffusion and Thermal Stability of Hydrogen in ZnO. Bang, J., Chang, K.J.: Applied Physics Letters, 2008, 92[13], 132109