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

Abstract

Temperature-dependent photoluminescence (PL) of ZnO layers grown on 6H-SiC substrates has been described. The PL spectra 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 D0X linewidth 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.