PHOTOLUMINESCENCE STUDIES OF GAN FILMS OF DIFFERENT BUFFER LAYER AND DOPING CONCENTRATION

Photoluminescence (PL) measurements of GaN films with various buffer t hicknesses and Si-doping concentrations have been carried out. PL resp onse of one specific sample was studied for temperature dependence. Th e results showed that the band gap energy reduction is linearly propor tional to the temperature increase with a slope of similar to-4 x 10(- 4) eV.K-1 and that the activation energies for donor-bound and accepto r-bound exciton transitions are 15 and 18 meV, respectively. In Si-dop ed GaN films, the PL data indicated that the reduced gap depends on th e third power of carrier concentration as n(1/3). We also obtained a c oncentration coefficient of 2.34 x 10(-4) eV.cm and a band gap energy of 3.426 eV in the undoped GaN film.