Characterization of CdTe substrates and MOCVD Cd_1-xZn_xTe epilayers

摘要

The quality of CdTe substrates and of Cd_1-xZn_xTe (x<=0.1) epilayers grown by metalorganic chemical vapor depositon (MOCVD) on CdTe substrates, were characterized by Raman scattering, by photoluminescence (PL) as well as by X-ray double crystal rocking curve (DCRC). At low temperature the Raman intensity of the LO phonon was enhanced wherever there was a structural defect. the quantitative measure of the structural perfection is related to the ratio between the defect band and excitonic peaks, and correlates with the X-ray full-width at half-maximum (FWHM) of the layer peak. It is shown that in addition to these parameters, the FWHM of the PL defect band is a useful parameter to determine the quality of the epilayer, and a good correlation is obtained between the different parameters. The effect of zinc partial pressure during growth and the reactor design are studied. The results indicate that crystalline imperfection is caused by lattice mismatch between the CdTe substrate and the CdZnTe epilayer and by the nonuniformity of the zinc composition throughout the layers. direct c 1999 Elsevier Science B.V. All rights reserved.