UNDERSTANDING THE NATURE OF SUPERLATTICE INTERFACE MODES BY MULTIPHONON RAMAN-SCATTERING

Multiphonon (MP) Raman spectra involving only the macroscopic interfac e (IF) modes in extra-short-period (GaAs)(4)/(AlAs)(2) AB/CB-type supe rlattice (SL) and the localized microscopic interface (LMIF) mode in ( CdSe)(4)/(ZnTe)(8) AB/CD SL are reported, The MP Raman spectra involvi ng only IF modes are attributed to the ability of electrons in the wel ts to penetrate into the barrier, The MP features of the LMIF mode wer e found to be completely different from those of the longitudinal opti cal (LO) bulk-like mode in the same sample. These novel MP features of the LMIF mode have been successfully explained by the anharmonic deca y theory of localized modes of defects, suggesting that the interface of AB/CD-type SLs can be considered as defects in SLs. In contrast, th e wavenumber and intensity behaviour of the MP spectra of the IF modes are similar to those of the LO modes, but the dependence of the linew idths on the order of the IF modes is reminescent of that of the LMIF mode, These behaviours indicate that the IF modes contain characterist ics of both the bulk-like LO mode and the LMIF mode.