Two-LO-phonon resonant Raman scattering in II-VI semiconductors

Recently, absolute values of second-order Raman scattering efficiency have been measured around the E(0) and E(0)+Delta(0) critical points of several II-VI semiconductor compounds. The measurements were performed in the z(x,x)(z) over bar backscattering configuration on (001) (ZnSe and ZnTe) and (1(1) over bar0$) (CdTe) surfaces. They show strong incoming and outgoing resonances around the band gap and larger scattering efficiencies as compared to III-V compounds. A theoretical model which includes excitons as intermediate states in the Raman process is shown to give a very good quantitative agreement between theory and experiment. Only a small discrepancy exists, while in III-V compounds the discrepancies were close to one order of magnitude. A discussion of the differences in the scattering efficiencies between II-VI and III-V compounds is also reported.