Selective excitation and thermal quenching of the yellow luminescence of GaN

We report the observation of narrower structures in the yellow luminescence of bulk and thin-film n-type GaN, using the technique of selective excitat ion. These fine structures exhibit thermal quenching associated with an act ivated behavior. We attribute these fine structures to phonons and electron ic excitations of a shallow donor-deep acceptor complex, and determine its activation energy for delocalization. Our results suggest that in addition to distant donor-acceptor pairs, the yellow luminescence can also involve e mission complexes of shallow donors and deep acceptors. (C) 1999 American I nstitute of Physics. [S0003-6951(99)04347-8].