Characterization of CdTe substrates and MOCVD Cd1-xZnxTe epilayers

The quality of CdTe substrates and of Cd1-xZnxTe (x less than or equal to 0 .1) epilayers grown by metalorganic chemical vapor deposition (MOCVD) on Cd Te substrates, were characterized by Raman scattering, by photoluminescence (PL) as well as by X-ray double crystal rocking curve (DCRC). At low tempe rature 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 c orrelates with the X-ray full-width at half-maximum (FWHM) of the layer pea k. It is shown that in addition to these parameters, the FWHM of the PL def ect band is a useful parameter to determine the quality of the epilayer, an d a good correlation is obtained between the different parameters. The effe ct of zinc partial pressure during growth and the reactor design are studie d. The results indicate that crystalline imperfection is caused by lattice mismatch between the CdTe substrate and the CdZnTe epilayer and by the nonu niformity of the zinc composition throughout the layers. (C) 1999 Elsevier Science B.V. All rights reserved.