Quantitative study of molecular N_2 trapped in disordered GaN:O films
  The structure of disordered GaN:O films grown by ion-assisted deposition is investigated using x-ray absorption near-edge spectroscopy and Raman spectroscopy. It is found that between 4 and 21 % of the nitrogen in the films is in the form of molecular N_2 that interacts only weakly with the surrounding matrix. The anion to cation ratio in the GaN:O host remains close to unity, and there is a close correlation between the N_2 fraction, the level of oxygen impurities, and the absence of short-range order in the GaN:O matrix. 
B.J. Ruck, A. Koo, U.D. Lanke, F. Budde, S. Granville, H.J. Trodahl   (1), A. Bittar (2), J.B. Metson (3), V.J. Kennedy, A. ...