Abstract
Cd x Zn 1−x Te epilayers were grown on GaAs(001) substrates by molecular-beam epitaxy. The optical properties of the epilayers were studied by taking reflectance (R) and photoluminescence (PL) measurements. From the R and PL spectra, the energy gaps of the epilayers were determined and shown to decrease as the Cd concentration increased. A quadratic equation that related the energy gap to Cd concentration was also derived. The dependence of the PL spectra on temperature was studied as well. A redshift of the PL peaks was observed as the temperature increased. The exciton activation energy of the epilayers was determined from the plots of integrated PL intensity versus temperature. It tends to decrease as the Cd content increased. The temperature dependence of the energy gaps, determined from the PL spectra, was fitted according to both Varshni’s and O’Donnell and Chen’s relations [Y. P. Varshni, Physica 34, 149 (1967); K. P. O’Donnell and X. Chen, Appl. Phys. Lett. 58, 2924 (1991)]. Good fits were obtained using both relations for the samples with small Cd concentration. However, the fitted O’Donnell’s curve for the Cd0.582Zn0.418Te epilayer shows a more reasonable trend as temperature increases.
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