X-ray double-crystal diffraction studies of CdTe/GaAs heteroepitaxial layers

The full width at half maximum (FWHM) of the rocking curves and its corresponding strains in CdTe epitaxial layers grown on (111) and (100) GaAs substrates with a metalorganic chemical vapor deposition (MOCVD) technique have been investigated by means of X-ray double-crystal diffractometry. The (333)CdTe rocking curves of (111)CdTe/(111)GaAs epilayers showed that the FWHM values decreased from 750 to 432 arc sec as the thickness increased from 0.5 to 1.8 μm. However, when the growth temperature was raised to 390°C, the epilayer growth mechanism changed from 2D to 3D fashion and the FWHM increased sharply to 1080 arc sec. Compressive strains were present in these (111)CdTe layers and were decreased with increasing thickness. The (400)CdTe rocking curves of (100)CdTe/(100)GaAs epilayers exhibited similar behavior to those of (333)CdTe peaks. Nevertheless, these (100) layers exhibited a 3D growth mechanism even at low growth temperatures (340°C). Epilayer morphologies in consistency with the proposed growth mechanism were also observed.