MgxZn1-xO films were grown on c-plane sapphire substrates by metal organic chemical vapour deposition. The effects of growth rate and low temperature (280ºC) ZnO buffer layer thickness on the incorporation efficiency of Mg as well as the optical and structural properties of the MgxZn1-xO films were investigated. Low growth rates enhance the segregation of Mg, leading to a magnesium rich region near the interface with the sapphire substrate. Hence, a shoulder is observed on the higher energy side of the main donor bound exciton in the photoluminescence spectrum. The effect of a ZnO buffer layer grown for 5 min and 10 min at 280ºC for MgxZn1-xO films with low Mg content (xv = 0.2) and for MgxZn1-xO with high Mg content (xv = 0.5) was also investigated. The ZnO buffer layer causes an improvement in the Mg incorporation but deteriorates the structural and optical properties for all the films. The MgxZn1-xO thin films grown on a thinner ZnO buffer layer showed the best optical and structural properties. Furthermore, the deposition of thin films on a ZnO buffer layer leads to an increase in lateral growth rate, which enhances the width of columnar grains. A ZnO buffer layer does not prevent the formation of a Mg rich interfacial layer.
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