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 atmosphe re. Activation energies of 26.5 and 230 meV were derived from temperature d ependent PL studies of the donor-acceptor (D-A) transitions. Furthermore, f or 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 predominan tly the wurtzite structure, with some evidence for cubic inclusions. We dis cuss 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. (C) 2001 Elsevier Science B.V. All rights reserved.