Study of molecular beam epitaxy of cadmium telluride on sapphire

The effect of thermal treatment of (0001) sapphire substrates on the structure of cadmium telluride films grown by molecular beam epitaxy was investigated. The growth process was carried out on a laboratory facility equipped with a mass spectrometer and electron diffractometer. It was established that no annealing or annealing in vacuum (P < 0.13 Pa) results in the growth of polycrystalline CdTe films. Epitaxial CdTe films with a cubic structure of the sphalerite type oriented with the (111) plane parallel to the substrate grow on the substrates annealed in air at T > 1000°C. Electron diffraction patterns showed that they have a mosaic structure and contain twins with the 〈111〉 twinning axis. Atomic-force microscopic images revealed CdTe crystallites with lateral sizes of ∼50 nm arranged along the steps on the sapphire substrate surface. These results allowed the conclusion to be drawn that the growth of CdTe on sapphire substrates can occur by the formation of the three-dimensional nucleation centers according to the Volmer-Weber mechanism.