EFFECTS OF SPONTANEOUS ORDERING ON RAMAN-SPECTRA OF GAINP2

The effects of spontaneous CuPtB ordering on the lattice dynamics of G aInP2 allays are studied by room-temperature Raman-scattering experime nts on a series of GaInP2 samples with various degrees of ordering, gr own by organometallic vapor phase epitaxy. In measurements on the (001 ) growth plane, we have observed several changes in the optical-phonon range of the Raman spectrum, the most notable of which is the emergen ce of an extra peak at 354 cm(-1). This peak is identified as a longit udinal-optical mode due to the superlattice effect In the ordered allo ys. The acoustic-phonon range of the (001) Raman spectra of the ordere d samples shows extra peaks at 60 and 205 cm(-1), which are identified as the folded transverse and longitudinal acoustic phonons, respectiv ely. For the optical phonons, the Raman selection rules and the identi fication of the extra peak are tested by measuring right-angle Raman s cattering. The results are consistent with the trigonal C-3v symmetry of the ordered alloys.