Temperature-dependent photoluminescence of CdZnO thin films grown by molecular-beam epitaxy

Large-Cd-concentration (Eg<3.0 eV) CdZnO thin films were grown using molecular-beam epitaxy. Variable-temperature photoluminescence measurements were performed on three typical CdZnO samples having pure wurtzite, pure rocksalt, and wurtzite–rocksalt mixture structures, respectively. The temperature dependence of the CdZnO bandgap shrinkage was investigated and analyzed based on the empirical Varshni and Bose–Einstein fitting on the near-band-edge photoluminescence peak positions. The temperature dependence of the integral PL intensity in the CdZnO samples was also fitted, where fitting equation with hopping term included shows a closer fit to the experimental data. The possible hopping processes in the CdZnO thin films may be related to the band tail states due to alloying effect and Cd distribution nonuniformity in the CdZnO samples.