CONFINED AND PROPAGATING PHONONS IN ULTRATHIN CDTE ZNTE SUPERLATTICES/

We report the occurrence of confined longitudinal-optical phonons in ( CdTe)n(ZnTe)n (n = 2, 3, and 5) short-period superlattices as observed in their Raman spectra, complementing the infrared reflectivity studi es in which confined transverse-optical phonons, were reported [Phys. Rev. B 47, 1998 (1993)]. The dispersion of ZnTe-LO phonons in these hi ghly strained superlattices, determined from the frequencies of the co nfined phonons, is in agreement with inelastic neutron scattering data on bulk ZnTe. The present study also reveals in these superlattices c onfined CdTe-LO phonons as well as folded acoustic phonons for n = 5.