Enhanced red emission from Eu-implanted ZnMgO layers and ZnO/ZnMgO quantum structures

Abstract

Photoluminescence (PL) of Eu3+ ions in single layers of ZnO and ZnMgO and in short-period ZnO/ZnMgO and ZnO/MgO superlattices (SLs) grown by molecular beam epitaxy was investigated, and the results have been presented. Single ZnO and ZnMgO layers were grown on GaN/sapphire substrates, whereas the SLs on c-oriented crystalline ZnO. All samples were implanted with 300 keV Eu ions, and then rapid thermal annealing was performed at 800 °C for 5 min in an oxygen atmosphere to activate the intra-4f-shell PL of Eu3+ ions. After annealing, the red emission due to the 5D0 → 7F2 radiative transitions of Eu3+ was observed at excitation above the energy gap. The results clearly show that Mg is essential for obtaining the high 4f–4f PL intensity of Eu3+ ions, as in ZnMgO layers and short period SLs, the red emission is several times more intense than in ZnO. The PL excitation spectra were examined to confirm the energy transfer from the bandgap to the Eu3+ ions. Clear evidence is presented that in the studied short period SLs, the excitation of the Eu3+ PL occurs via generation of excitons in the barrier layers.