Photoluminescence characteristics of Mg- and Si-doped GaN thin films grownby MOCVD technique

We have studied the optical structural and surface morphology of doped and undoped GaN thin films. The p- and n-type thin films have been successfully prepared by low-pressure MOCVD technique by doping with Mg and Si, respect ively. The different carrier concentrations were obtained in the GaN thin f ilms by Varying dopant concentrations. Photoluminescence (PL) studies were carried to find the defect levels in the doped and undoped GaN thin films a t low temperature. In the undoped GaN thin films, a low intensity and broad yellow band peak was observed. The donor-acceptor pair (DAP) emission and its phonon replicas were observed in both the Si or Mg lightly doped GaN th in films. The dominance of the blue and the yellow emissions increased in t he PL spectra, as the carrier concentration was increased. The XRD and SEM analyses were employed to study the structural and surface morphology of th e films, respectively. Both the doped and the undoped films exhibited hexag onal structure and polycrystalline nature. Mg-doped GaN thin films showed c olumnar structure whereas Si-doped films exhibited spherical shape grains. (C) 2000 Published by Elsevier Science B.V.