RAMAN-SCATTERING STUDY OF LONGITUDINAL ACOUSTIC AND OPTIC PHONONS IN INSB IN(1-X)AL(X)SB STRAINED-LAYER SUPERLATTICES/

Detailed scattering studies of InSb/In1-(x)Al(x)Sb (0.15 < x < 0.5) st rained-layer superlattices grown by magnetron sputter epitaxy on (001) InSb substrates are reported for the first time. A number of folded a coustic phonones appear in the Raman spectra and their frequencies are accurately predicted by Rytov's theory of acoustic vibrations in laye red media. The longitudinal optic phonons in the In1-(x)Al(x)Sb layers exhibit two-mode behavior and their shift due to tjhe intralayer stri an is discussed. Resonant Raman scattering was used to probe the elect ronic structure in the region of the E1 and E1 + DELTA1 optical gaps. The two sets of peaks observed in the plots of the Raman cross section section vs photon energy are shown to originate from the independent electronic transitions in the alternating layers. estimates of the str ain and confinement effects were made and these agree with the observe d differences from bulk material.