Observation of blue shifts in ZnO/ZnMgO multiple quantum well structures by ion-implantation induced intermixing

Abstract

Implantation with low-energy (80 keV) oxygen ions and subsequent rapid thermal annealing at 800 °C are used to induce intermixing in a stack of 19 ZnO/Zn0.7Mg0.3O multiple quantum wells grown on sapphire by molecular beam epitaxy. Large blue shifts of more than 300 meV have been observed for doses up to 1 × 1016 cm−2, with no observation of saturation. This process is driven by the creation of defects by implantation which encourage the diffusion of Mg from the barrier layers into the ZnO quantum wells. Although defects are introduced during the implantation process, good recovery of the cathodoluminescence is seen following rapid thermal annealing. The Zn–Mg interdiffusion in this system has also been calculated for the corresponding ion doses, and the diffusion coefficient extracted. This study has significant implications for band gap engineering of ZnO/ZnMgO optoelectronic devices.