Temperature-dependent photoluminescence of ZnO layers grown on 6H-SiC substrates

Temperature-dependent photoluminescence(PL) of ZnO layers grown on 6H-SiC substrates has been described. The PLspectra were dominated by free exciton (FX) emission throughout the whole temperature range, which reflects shallow nonradiative centers in high crystalline ZnO layers. The temperature-dependent exciton peak energy as well as intensity quenching due to overlapping of FX and D⁰X (donor-bound exciton) bands has been addressed with an inclusion of donor-bound exciton-like defects. The D⁰Xlinewidth of ∼8 meV exhibited the thermal activation energy of ∼16 meV, closely consistent with the exciton-defect binding energy. This particular bound-exciton peak suggests that it dissociates into a FX and a neutral-donor-bound-like defects pair complex with the increase of temperature.This work was supported in part by the Special Postdoctoral Research Fellowship Program, Photodynamics Research Center, The Institute of Physical and Chemical Research, Japan