Photoluminescence study of GaN grown by pulsed laser deposition in nitrogen atmosphere

Low temperature photoluminescence measurements were performed on thin films of gallium nitride grown by pulsed laser deposition in a nitrogen atmosphere. Activation energies of 26.5 and 230 meV were derived from temperature dependent PL studies of the donor–acceptor (D–A) transitions. Furthermore, for the 3.41 eV line, two values of activation energy (13.5 and 25 meV) were observed at low and high temperatures. X-ray diffraction showed predominantly the wurtzite structure, with some evidence for cubic inclusions. We discuss these data in terms of the possibility of a mixed phase structure and examine evidence for the localization of the electrons and holes in the two phases.