Photoluminescence properties of ZnO/Zn0.9Mg0.1O multi-quantum wells with different well widths

Temperature-dependent photoluminescence (PL) properties of ZnO/Zn0.9Mg0.1O multi-quantum wells (MQWs) grown on Si (1 1 1) substrates by pulsed laser deposition have been investigated. For MQWs with well widths of 14 and 3 nm, the predominant excitonic emission in the whole temperature range (8-300 K) is attributed to bound excitons and localized excitons, respectively. The effect of quantum confinement on enhancing the intensity of the excitonic emission is clearly observed in the MQWs with well width of 3 nm, while the effect on blue-shifting the emission energy is not distinct, most probably due to the quantum confined Stark effect. The PL peak from the barrier layers shows an 'S'-shaped shift with increasing temperature due to localization of carriers in the potential minima induced by composition and interface fluctuations. The depth of the potential well is determined to be ∼15 meV