ZnO/MgZnO p–n junction light-emitting diodes fabricated on sapphire substrates by pulsed laser deposition technique

A ZnO/MgZnO p–n junction light-emitting diode employing a [ZnO/Mg0.1Zn0.9O] multiple quantum well active layer was fabricated on a c-plane sapphire substrate by the pulsed laser deposition technique. Phosphorous and gallium were used for p-type and n-type doping, respectively. Sapphire substrates were annealed in N2 ambient at 1200 °C prior to the deposition of p-type ZnO layer. Structural characterization of the P-doped ZnO layer was performed and excellent lattice matching with sapphire was obtained. The ZnO/MgZnO-based LED showed efficient electroluminescence at room temperature with bias voltages ⩾7 V. The as-fabricated LEDs were found to be sensitive to ambient air and degraded after some hours, possibly due to the formation of a surface conduction layer. LEDs can be further reactivated by annealing at 400 °C in ambient O2.