PHOTOLUMINESCENCE STUDY OF NANO-CRYSTALLINE GAN AND ALN GROWN BY REACTIVE SPUTTERING

Nanocrystallite GaN and ALN (nc-GaN and nc-AlN) films have been made b y reactive sputtering and were studied by photoluminescence (PL), abso rption coefficient and X-ray diffraction measurements. A yellow PL is observed in nc-GaN films. The PL spectrum has two broad peaks with ene rgies of 2.8 eV and 2.4 eV. The optical gap (E-04) is about 3.2 eV and the Urbach tail energy is 335 meV. A PL peak at 2.8 eV disappeared af ter annealing at 400 degrees C and 600 degrees C. After annealing at 8 00 degrees C, the PL peak at 2.8 eV recovered again. The changes of PL intensity are explained by the creation of recombination centers. Hyd rogenation of GaN did not occur by H-2 plasma treatment. The optical g ap (E-04) of the AlN film is about 4.8 eV. The absorption coefficient spectrum has an exponential tail region with the Urbach tail energy of 674 meV, but photoluminescence was not observed. (C) 1998 Elsevier Sc ience B.V. All rights reserved.