Structural characterization of CdTe layers grown on (0001) sapphire by MOCVD

We report on the growth of CdTe layers directly onto (0001) sapphire substrates by MOCVD. The structure and morphology of the layers have been investigated as a function of growth temperature and II/VI precursor molar ratio by X-ray diffraction and scanning electron microscopy. The texture of the samples has revealed the existence of a temperature threshold, with higher growth temperatures resulting on completely (111) oriented layers. Some of these layers contained microtwins, as indicated by the extra peaks in the {422} Phi scans, leading to the existence of two different domains. The structural quality of each domain, as well as of the sample as a whole, has been determined by measuring rocking curves of asymmetric and symmetric reflections, respectively. It has been found that the presence of twins can be suppressed by employing growth temperatures around 415degreesC and Cd-rich conditions. These twin-free layers exhibit a uniform faceted surface and a (333) rocking curve width of 162 arcs, indicating a good crystalline quality. (C) 2004 Elsevier B.V. All rights reserved.