Résumé
Raman measurements are used to probe the built-in strain due to the large lattice mismatch in two short-period ZnSe-ZnTe superlattices. In the largest period structure, local information on confinement and strain effects in the different layers is deduced from the LO phonon frequencies. An estimate of the in-plane strain gives evidence of a partial relaxation of both layers; in this structure, folded acoustical phonons are clearly observed under resonant conditions. The Raman spectra of the shortest period superlattice are characterized by a unique structure assigned to an unusual propagative mode resulting from the overlap of the optical bands of the two constituents.