Yellow luminescence inn-type GaN epitaxial films

Photoluminescence, resonant Raman scattering, and photoconductivity measurements have been employed to study the yellow emission in undoped $n$-type and a set of Se-doped GaN epitaxial films. It is best described by a transition from the conduction-band edge to a deep acceptor. Unlike the donors and acceptors used in most previous studies that substitute Ga sites, Se atoms can replace N sites. With this unique fact, we identify that the origin of the yellow emission involves the nitrogen antisite. In addition, it is found that persistent photoconductivity can be observed after the yellow band excitation. We further suggest that the nitrogen antisite exhibits a metastable behavior similar to the arsenic antisite in GaAs.