A comparative study on electroluminescence from ZnO-based double heterojunction light emitting diodes grown on different lattice mismatch substrates

We have comparatively investigated the electroluminescence (EL) performance from the asymmetric p-Mg0.05Zn0.95O/i-ZnO/n+-GaN and p-Mg0.05Zn0.95O/i-ZnO/n+-Si double-heterojunction light emitting diodes (LEDs) grown on different lattice mismatch substrates. The I-V curve measurements show clear rectification characteristics with a threshold voltage of 3.8 and 6 V for the p-Mg0.05Zn0.95O/i-ZnO/n+-GaN and p-Mg0.05Zn0.95O/i-ZnO/n+-Si double heterojunctions, respectively. A strong violet-ultraviolet EL emission and no deep-level emission were observed for the p-Mg0.05Zn0.95O/i-ZnO/n+-GaN double heterojunction grown on small lattice-mismatched n+-GaN substrate. In comparison, a dominant visible emission band and a weak ultraviolet emission peak were observed for p-Mg0.05Zn0.95O/i-ZnO/n+-Si double heterojunction grown on large lattice-mismatched n+-Si substrate. The difference between both LEDs is due to different quality of the MgZnO and ZnO layers grown on different lattice mismatch substrates.