Equilibrium state of hydrogen in gallium nitride: Theory and experiment - Myers, S. M.; Wright, A. F.; Petersen, G. A.; Seager, C. H.; Wampler, W. R.; Crawford, M. H.; Han, J. (American Institute of Physics (AIP), 2000)
http://dx.doi.org/10.1063/1.1309123
Keywords: U