GALLIUM VACANCIES AND THE YELLOW LUMINESCENCE IN GAN

We have investigated native defects and native defect-impurity complex es as candidate sources for the yellow luminescence in GaN. Using stat e-of-the-art first-principles calculations, we find strong evidence th at the Ga vacancy (V-Ga) is responsible. The dependence of the V-Ga fo rmation energy on Fermi level explains why the yellow luminescence is observed only in n-type GaN. The V-Ga defect level is a deep acceptor state, consistent with recent pressure experiments. Finally we show th at the formation of V-Ga is enhanced by the creation of complexes betw een V-Ga and donor impurities. (C) 1996 American Institute of Physics.